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ABOUT  THE 
WEATHER 


HARRINGTON 


LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 

Class 


Hppletona'  1bome  IReaJnng 

EDITED    BY 
WILLIAM  T.   HARRIS,   A.M.,   LL.  D. 

UNITED  STATES  COMMISSIONER  OF  EDUCATION 


DIVISION   I 

NATURAL  HISTORY 


DR.    JULIUS   HANN, 
Director  of  the  Austrian  Meteorological  Service. 


APPLETONS'  HOME  READING  BOOKS 


ABOUT  THE  WEATHER 


BY 


MARK  W.   HARRINGTON 


NEW   YORK 
D.    APPLETON    AND    COMPANY 

1909 


COPYRIGHT,  1899, 
B*  D.  APPLETON  AND  COMPANY. 


INTRODUCTION  TO  THE  HOME  HEADING 
BOOK  SERIES  BY  THE  EDITOR. 


THE  new  education  takes  two  important  direc- 
tions— one  of  these  is  toward  original  observation, 
requiring  the  pupil  to  test  and  verify  what  is  taught 
him  at  school  by  his  own  experiments.  The  infor- 
mation that  he  learns  from  books  or  hears  from  his 
teacher's  lips  must  be  assimilated  by  incorporating  it 
with  his  own  experience. 

The  other  direction  pointed  out  by  the  new  edu- 
cation is  systematic  home  reading.  It  forms  a  part  of 
school  extension  of  all  kinds.  The  so-called  "  Univer- 
sity Extension  "  that  originated  at  Cambridge  and  Ox- 
ford has  as  its  chief  feature  the  aid  of  home  reading  by 
lectures  and  round-table  discussions,  led  or  conducted 
by  experts  who  also  lay  out  the  course  of  reading. 
The  Chautauquan  movement  in  this  country  prescribes 
a  series  of  excellent  books  and  furnishes  for  a  goodly 
number  of  its  readers  annual  courses  of  lectures.  The 
teachers'  reading  circles  that  exist  in  many  States  pre- 
scribe the  books  to  be  read,  and  publish  some  analysis, 
commentary,  or  catechism  to  aid  the  members. 

Home  reading,  it  seems,  furnishes  the  essential 
basis  of  this  great  movement  to  extend  education 


212418 


vi  ABOUT  THE   WEATHER. 

beyond  the  school  and  to  make  self -culture  a  habit 
of  life. 

Looking  more  carefully  at  the  difference  between 
the  two  directions  of  the  new  education  we  can  see 
what  each  accomplishes.  There  is  first  an  effort  to 
train  the  original  powers  of  the  individual  and  make 
him  self -active,  quick  at  observation,  and  free  in  his 
thinking.  Next,  the  new  education  endeavors,  by  the 
reading  of  books  and  the  study  of  the  wisdom  of  the 
race,  to  make  the  child  or  youth  a  participator  in  the 
results  of  experience  of  all  mankind. 

These  two  movements  may  be  made  antagonistic 
by  poor  teaching.  The  book  knowledge,  containing  as 
it  does  the  precious  lesson  of  human  experience,  may 
be  so  taught  as  to  bring  with  it  only  dead  rules  of 
conduct,  only  dead  scraps  of  information,  and  no 
stimulant  to  original  thinking.  Its  contents  may  be 
memorized  without  being  understood.  On  the  other 
hand,  the  self -activity  of  the  child  may  be  stimulated 
at  the  expense  of  his  social  well-being — his  originality 
may  be  cultivated  at  the  expense  of  his  rationality. 
If  he  is  taught  persistently  to  have  his  own  way,  to 
trust  only  his  own  senses,  to  cling  to  his  own  opinions 
heedless  of  the  experience  of  his  fellows,  he  is  pre- 
paring for  an  unsuccessful,  misanthropic  career,  and 
is  likely  enough  to  end  his  life  in  a  madhouse. 

It  is  admitted  that  a  too  exclusive  study  of  the 
knowledge  found  in  books,  the  knowledge  which  is 
aggregated  from  the  experience  and  thought  of  other 
people,  may  result  in  loading  the  mind  of  the  pupil 
with  material  which  he  can  not  use  to  advantage. 


EDITOR'S   INTRODUCTION.  vii 

Some  minds  are  so  full  of  lumber  that  there  is  no 
space  left  to  set  up  a  workshop.  The  necessity  of 
uniting  both  of  these  directions  of  intellectual  activity 
in  the  schools  is  therefore  obvious,  but  we  must  not, 
in  this  place,  fall  into  the  error  of  supposing  that  it  is 
the  oral  instruction  in  school  and  the  personal  influ- 
ence of  the  teacher  alone  that  excites  the  pupil  to  ac- 
tivity. Book  instruction  is  not  always  dry  and  theo- 
retical. The  very  persons  who  declaim  against  the 
book,  and  praise  in  such  strong  terms  the  self -activity 
of  the  pupil  and  original  research,  are  mostly  persons 
who  have  received  their  practical  impulse  from  read- 
ing the  writings  of  educational  reformers.  Yery  few 
persons  have  received  an  impulse  from  personal  con- 
tact with  inspiring  teachers  compared  with  the  num- 
ber that  have  been  aroused  by  reading  such  books  as 
Herbert  Spencer's  Treatise  on  Education,  Rousseau's 
Emile,  Pestalozzi's  Leonard  and  Gertrude,  Francis 
W.  Parker's  Talks  about  Teaching,  G.  Stanley 
Hall's  Pedagogical  Seminary.  Think  in  this  connec- 
tion, too,  of  the  impulse  to  observation  in  natural  sci- 
ence produced  by  such  books  as  those  of  Hugh  Miller, 
Faraday,  Tyndall,  Huxley,  Agassiz,  and  Darwin. 

The  new  scientific  book  is  different  from  the  old. 
The  old  style  book  of  science  gave  dead  results  where 
the  new  one  gives  not  only 'the  results,  but  a  minute 
account  of  the  method  employed  in  reaching  those  re- 
sults. An  insight  into  the  method  employed  in  dis- 
covery trains  the  reader  into  a  naturalist,  an  historian, 
a  sociologist.  The  books  of  the  writers  above  named 
have  done  more  to  stimulate  original  research  on  the 


viii  ABOUT  THE   WEATHER. 

part  of  their  readers  than  all  other  influences  com- 
bined. 

It  is  therefore  much  more  a  matter  of  importance 
to  get  the  right  kind  of  book  than  to  get  a  living 
teacher.  The  book  which  teaches  results,  and  at  the 
same  time  gives  in  an  intelligible  manner  the  steps  of 
discovery  and  the  methods  employed,  is  a  book 
which  will  stimulate  the  student  to  repeat  the  ex- 
periments described  and  get  beyond  them  into  fields 
of  original  research  himself.  Every  one  remem- 
bers the  published  lectures  of  Faraday  on  chemistry, 
which  exercised  a  wide  influence  in  changing  the 
style  of  books  on  natural  science,  causing  them  to 
deal  with  method  more  than  results,  and  thus  train 
the  reader's  power  of  conducting  original  research. 
Robinson  Crusoe  for  nearly  two  hundred  years  has 
aroused  the  spirit  of  adventure  and  prompted  young 
men  to  resort  to  the  border  lands  of  civilization.  A 
library  of  home  reading  should  contain  books  that  in- 
cite to  self-activity  and  arouse  the  spirit  of  inquiry. 
The  books  should  treat  of  methods  of  discovery  and 
evolution.  All  nature  is  unified  by  the  discovery  of 
the  law  of  evolution.  Each  and  every  being  in  the 
world  is  now  explained  by  the  process  of  development 
to  which  it  belongs.  Every  fact  now  throws  light  on 
all  the  others  by  illustrating  the  process  of  growth  in 
which  each  has  its  end  and  aim. 

The  Home  Eeading  Books  are  to  be  classed  as 
follows : 

First  Division.  Natural  history,  including  popular 
scientific  treatises  on  plants  and  animals,  and  also  de- 


EDITOR'S  INTRODUCTION.  ix 

scriptions  of  geographical  localities.  The  branch  of 
study  in  the  district  school  course  which  corresponds 
to  this  is  geography.  Travels  and  sojourns  in  distant 
lands;  special  writings  which  treat  of  this  or  that 
animal  or  plant,  or  family  of  animals  or  plants ;  any- 
thing that  relates  to  organic  nature  or  to  meteorol- 
ogy, or  descriptive  astronomy  may  be  placed  in  this 
^lass. 

Second  Division.  Whatever  relates  to  physics  or 
natural  philosophy,  to  the  statics  or  dynamics  of  air  or 
water  or  light  or  electricity,  or  to  the  properties  of 
matter ;  whatever  relates  to  chemistry,  either  organic 
or  inorganic — books  on  these  subjects  belong  to  the 
class  that  relates  to  what  is  inorganic.  Even  the  so- 
called  organic  chemistry  relates  to  the  analysis  of 
organic  bodies  into  their  inorganic  compounds. 

Third  Division.  History,  biography,  and  ethnol- 
ogy. Books  relating  to  the  lives  of  individuals;  to 
the  social  life  of  the  nation ;  to  the  collisions  of  na- 
tions in  war,  as  well  as  to  the  aid  that  one  nation 
gives  to  another  through  commerce  in  times  of  peace ; 
books  on  ethnology  relating  to  the  modes  of  life  of 
savage  or  civilized  peoples ;  on  primitive  manners 
and  customs — books  on  these  subjects  belong  to  the 
third  class,  relating  particularly  to  the  human  will, 
not  merely  the  individual  will  but  the  social  will, 
the  will  of  the  tribe  or  nation;  and  to  this  third 
class  belong  also  books  on  ethics  and  morals,  and 
on  forms  of  government  and  laws,  and  what  is  in- 
cluded under  the  term  civics,  or  the  duties  of  citi- 
zenship. 


X  ABOUT  THE   WEATHER. 

Fourth  Division.  The  fourth  class  of  books  in- 
cludes more  especially  literature  and  works  that  make 
known  the  beautiful  in  such  departments  as  sculpture, 
painting,  architecture  and  music.  Literature  and  art 
show  human  nature  in  the  form  of  feelings,  emotions, 
and  aspirations,  and  they  show  how  these  feelings 
lead  over  to  deeds  and  to  clear  thoughts.  This  de- 
partment of  books  is  perhaps  more  important  than 
any  other  in  our  home  reading,  inasmuch  as  it  teaches 
a  knowledge  of  human  nature  and  enables  us  to  un- 
derstand the  motives  that  lead  our  fellow-men  to 
action. 

PLAN  FOB  USE  AS  SUPPLEMENTARY  BEADING. 

The  first  work  of  the  child  in  the  school  is  to 
learn  to  recognize  in  a  printed  form  the  words  that 
are  familiar  to  him  by  ear.  These  words  constitute 
what  is  called  the  colloquial  vocabulary.  They  are 
words  that  he  has  come  to  know  from  having  heard 
them  used  by  the  members  of  his  family  and  by  his 
playmates.  He  uses  these  words  himself  with  con- 
siderable skill,  but  what  he  knows  by  ear  he  does  not 
yet  know  by  sight.  It  will  require  many  weeks, 
many  months  even,  of  constant  effort  at  reading  the 
printed  page  to  bring  him  to  the  point  where  the 
sight  of  the  written  word  brings  up  as  much  to  his 
mind  as  the  sound  of  the  spoken  word.  But  patience 
and  practice  will  by  and  by  make  the  printed  word 
far  more  suggestive  than  the  spoken  word,  as  every 
scholar  may  testify. 

In  order  to  bring  about  this  familiarity  with  the 


EDITOR'S  INTRODUCTION. 


XI 


printed  word  it  has  been  found  necessary  to  re-en- 
force the  reading  in  the  school  by  supplementary 
reading  at  home.  Books  of  the  same  grade  of  diffi- 
culty with  the  reader  used  in  school  are  to  be  pro- 
vided for  the  pupil.  They  must  be  so  interesting 
to  him  that  he  will  read  them  at  home,  using  his  time 
before  and  after  school,  and  even  his  holidays,  for 
this  purpose. 

But  this  matter  of  familiarizing  the  child  with  the 
printed  word  is  only  one  half  of  the  object  aimed  at 
by  the  supplementary  home  reading.  He  should 
read  that  which  interests  him.  He  should  read  that 
which  will  increase  his  power  in  making  deeper 
studies,  and  what  he  reads  should  tend  to  correct  his 
habits  of  observation.  Step  by  step  he  should  be 
initiated  into  the  scientific  method.  Too  many  ele- 
mentary books  fail  to  teach  the  scientific  method  be- 
cause they  point  out  in  an  unsystematic  way  only 
those  features  of  the  object  which  the  untutored 
senses  of  the  pupil  would  discover  at  first  glance.  It 
is  not  useful  to  tell  the  child  to  observe  a  piece  of 
chalk  and  see  that  it  is  white,  more  or  less  friable, 
and  that  it  makes  a  mark  on  a  fence  or  a  wall.  Sci- 
entific observation  goes  immediately  behind  the  facts 
which  lie  obvious  to  a  superficial  investigation. 
Above  all,  it  directs  attention  to  such  features  of  the 
object  as  relate  it  to  its  environment.  It  directs  at- 
tention to  the  features  that  have  a  causal  influence  in 
making  the  object  what  it  is  and  in  extending  its 
effects  to  other  objects.  Science  discovers  the  recip- 
rocal action  of  objects  one  upon  another. 


xii  ABOUT  THE  WEATHER. 

After  the  child  has  learned  how  to  observe  what 
is  essential  in  one  class  of  objects  he  is  in  a  measure 
fitted  to  observe  for  himself  all  objects  that  resemble 
this  class.  After  he  has  learned  how  to  observe  the 
seeds  of  the  milkweed,  he  is  partially  prepared  to 
observe  the  seeds  of  the  dandelion,  the  burdock,  and 
the  thistle.  After  he  has  learned  how  to  study  tho 
history  of  his  native  country,  he  has  acquired  some 
ability  to  study  the  history  of  England  and  Scotland 
or  France  or  Germany.  In  the  same  way  the  daily 
preparation  of  his  reading  lesson  at  school  aids  him 
to  read  a  story  of  Dickens  or  Walter  Scott. 

The  teacher  of  a  school  will  know  how  to  obtain 
a  small  sum  to  invest  in  supplementary  reading.  In 
a  graded  school  of  four  hundred  pupils  ten  books  of 
each  number  are  sufficient,  one  set  of  ten  books  to  be 
loaned  the  first  week  to  the  best  pupils  in  one  of  the 
rooms,  the  next  week  to  the  ten  pupils  next  in  ability. 
On  Monday  afternoon  a  discussion  should  be  held 
over  the  topics  of  interest  to  the  pupils  who  have 
read  the  book.  The  pupils  who  have  not  yet  read 
the  book  will  become  interested,  and  await  anxiously 
their  turn  for  the  loan  of  the  desired  volume.  Another 
set  of  ten  books  of  a  higher  grade  may  be  used  in  the 
same  way  in  a  room  containing  more  advanced  pupils. 
The  older  pupils  who  have  left  school,  and  also  the 
parents,  should  avail  themselves  of  the  opportunity  to 
read  the  books  brought  home  from  school.  Thus  is 
begun  that  continuous  education  by  means  of  the  pub- 
lic library  which  is  not  limited  to  the  school  period, 
but  lasts  through  life.  W.  T.  HARRIS. 

WASHINGTON,  D.  C.,  Nov.  16,  1896. 


PKEFACE. 


NOTHING  a  few  years  ago  seemed  to  us  more 
capricious  and  lawless  than  the  weather.  The 
winds  blew  where  they  pleased,  and  no  one 
could  tell  whence  they  came  or  whither  they 
went.  And  yet,  like  all  other  phases  of  nature, 
the  weather  has  laws — uniform,  unchanging, 
and  inflexible — which  it  must  and  does  obey. 

Short  as  the  time  has  been  since  the  weather 
has  been  studied  as  a  science,  many,  though 
by  no  means  all,  of  these  laws  have  been  dis- 
covered ;  and  a  knowledge  of  them  is,  without 
doubt,  not  only  of  considerable  interest,  but  of 
the  greatest  possible  utility.  Without  dwelling 
upon  a  thousand  and  one  pleasures  that  are 
contingent  upon  a  correct  forecast  of  the  weather 
—cycling,  boating,  driving,  and  the  like — the 
builder,  the  sailor,  and  the  farmer  learn  that 
not  prosperity  alone  but  life  itself  sometimes 


xiv  ABOUT  THE  WEATHER. 

depends  upon  ability  to  perceive  and  under- 
stand warnings  given  by  science  and  nature  of 
what  is,  within  the  next  few  hours,  to  be  ex- 
pected of  the  elements. 

It  is  a  matter  of  vital  importance  to  the 
people  who  live  in  tracts  of  country  traversed 
by  the  fearfully  destructive  cyclones  that  an- 
nually visit  the  Western  parts  of  the  United 
States  to  be  able  to  detect  the  coming  of  one 
of  these  terrible  tempests  long  enough  to  in- 
sure the  safety  of  themselves  and  of  their  prop- 
erty. To  do  this  properly  requires  no  long 
apprenticeship,  no  great  amount  of  arduous 
study  of  the  subject.  It  is  safe  to  say  that 
within  the  covers  of  even  so  small  and  unpre- 
tending a  work  as  the  present  one,  written  as 
it  is  by  the  well-known  author  who  has  made  a 
lifelong  study  of  the  weather,  everything  essen- 
tial to  taking  practical  advantage  of  all  that  is 
now  known  on  the  topic  is  to  be  found. 

The  more  than  twelve  hundred  thousand  dol- 
lars expended  every  year  by  the  Government 
may  perhaps  be  considered  an  exorbitant  price 
to  pay  for  learning  what  weather  we  are  likely 
to  have  for  the  coming  twenty -four  hours ;  but 


PREFACE.  XV 

the  truth  is  that  no  public  investment  is  so  im- 
mediately and  so  immensely  profitable  as  that 
applied  to  the  maintenance  of  the  Weather 
Bureau. 

Not  only  are  the  cyclones  in  the  West,  but 
the  floods  of  streams  and  rivers,  especially 
those  of  the  Mississippi  Valley,  are  foretold, 
"  and  incalculable  saving  of  life  and  property," 
as  Mr.  J.  E.  Prindle  says  in  a  report  on  the  sub- 
ject, "result  from  their  warnings.  Before  the 
days  of  the  bureau,"  he  proceeds,  "the  West 
India  hurricanes  came  unannounced,  and  some- 
times two  thousand  lives  were  lost  in  a  single 
storm.  Under  the  warnings  of  the  Weather 
Bureau  three  such  storms  have  passed  in  suc- 
cession without  the  loss  of  a  single  life,  and 
the  property  destroyed  in  one  storm  would 
support  the  service  for  two  years.  At  Buffalo, 
in  the  winter  of  1895-'96,  by  forecasting  six 
very  severe  storms,  one  hundred  and  fifty  ves- 
sels, valued  at  seventeen  million  dollars  and 
carrying  eighteen  hundred  persons,  were  held 
safely  in  port  by  the  warnings," 

But  it  is  useless  to  multiply  examples  of 
this  kind  ;  they  are  constantly  occurring. 


xvi  ABOUT  THE   WEATHER. 

In  the  theory  of  education,  which  above  all 
aims  to  be  practical  in  selecting  branches  of 
instruction  that  are  best  fitted  to  be  turned  to 
account  in  life  and  experience,  a  study  of  the 
art  of  forecasting  the  weather  must  naturally 
hold  a  high  place ;  and,  indeed,  in  any  system 
of  education  few  fields  of  scientific  investiga- 
tion offer  more  interesting  and  valuable  results 
in  teaching  close  and  discriminating  observa- 
tion of  nature  and  in  reasoning  out  and  draw- 
ing logical  conclusions  from  given  premises  than 
does  this  study. 


CONTENTS. 


CHAPTER  PAGE 

I. — CONTEST  OF  MANKIND  WITH  THE  WEATHER  .        .  1 

II. — THE   WEATHER   CONQUEST   NOT   AN   UNMIXED   BENE- 
FIT             9 

III. — THE  INCOMPLETENESS   OF  THE  WEATHER  CONQUEST  17 

IV. — REMEDIES  AGAINST  INJURIES  BY  WEATHER    .        .  22 
V. — THE  PRESSURE  OF  THE  AIR  AND  HOW  IT  is  MEAS- 
URED   .        . 33 

VI. — CHANGES  IN  THE  PRESSURE  OF  THE  AIR       .        .  41 

VII. — THE  WINDS  :  THEIR  KINDS  AND  DISTRIBUTION       .  48 
VIII. — DIRECTION,  VELOCITY,  AND  MEASUREMENT  OP  THE 

WINDS  .       ^. 56 

IX. — THE  TEMPERATURE  OF  THE  AIR     ....  60 

X. — HUMIDITY,  OR  MOISTURE 66 

XI. — DEW,   FOG,   AND  CLOUD 73 

XII. — PRECIPITATION:  RAIN  AND  SNOW  ....  92 

XIII. — GENERAL  STORMS,  CYCLONES,  OR  LOWS  .  99 

XIV. — THE  CYCLONE  AS  A  STEAM  ENGINE  .  .  .  110 

XV. — CYCLONES  TRAVEL  EASTWARD        ....  117 

XVI. — THE   WEATHER   BROUGHT   BY   THE   CYCLONE      .           .  128 

XVII. — EFFECTS  OF  THE  EARTH'S  ROTATION      .        .        .  136 

XVIII. — ANTICYCLONES,  OR  HIGHS       .                       .        .  142 

XIX. — BETWIXT-AND-BETWEEN  WEATHER  .        .       .        .  148 

XX. — TORNADOES  OR  INTENSE  LOCAL  WHIRLS         .       .  156 

XXI. — STORMS  OF  ICE,  SLEET,  BALL  SNOW,  AND  HAIL      .  166 

xvii 


ABOUT  THE   WEATHER. 


CHAPTER  PAGE 

XXII.  —  THUNDERSTORMS  AND  CLOUD-BURSTS      .        .        .174 

XXIII.  —  LIGHTNING  AND  THUNDER      .....     180 

XXIV.  —  THE  WEATHER   PROGRESS   THROUGH   THE   DAY   AND 

YEAR      .........       187 

XXV.  —  LOCAL  INFLUENCES  ON  WEATHER   ....    194 
XXVI.  —  WEATHER    PREDICTIONS    AS   A   REMEDY   AGAINST 

WEATHER    INJURIES         ......      203 

XXVII.  —  THE  PROGRESS  OF  KNOWLEDGE  OF  THE   WEATHER    211 

XXVIII.  —  EXPERIMENTING  WITH  THE  AIR      .        .        .        .    223 

XXIX.  —  SIMPLE  RESULTS  OF  WEATHER  CHANGES  ,    232 


LIST  OF  ILLUSTKATIOISTS. 


An  Omaha  dwelling v     .  5 

Japanese  cooly's  hat  and  straw  coat        .        .        .     _ •'*       .  6 

Accumulation  of  hoarfrost  on  Mt.  Washington  in  winter      .  24 

A  locomotive  snowplow 28 

The  suction  effects  of  air  pressure  in  the  old-fashioned  cup- 
ping practiced  by  doctors 36 

Pump 37 

Air  pressure  upward.    Inverted  tumbler  kept  from  empty- 
ing by  a  piece  of  paper 38 

The  mercurial  barometer 39 

The  aneroid  barometer 40 

A  summer  dust-whirl 50 

Heat  equator  wanderings 52 

Rings  and  caps  of  the  earth  as  shown  in  the  winds        .        .  54 

Robinson's  cup  anemometer 57 

Finding  the  height  of  clouds 80 

Cirrus .        .        .        .82 

Cumulus 83 

Cirro-cumulus 84 

Wave  form 86 

Stratus 88 

Alto-cumulus 89 

Typical  overgrown  cumulus 90 

Double-turreted  cumulus 92 

Snow  crystals 95 

Weather  map 101 

Inflowing  winds  of  a  cyclone 104 

Scheme  of  vertical  currents  about  a  great  conflagration        .  106 

xix 


xx  ABOUT  THE  WEATHER. 

PAGE 

Section  of  a  cyclone  at  the  center  and  through  the  axis        .  115 
The  course  of  a  cyclone  across  the  United  States  .        .        .119 
The  way  general  storms  cross  South  America        .        .        .  122 
To  show  how  cyclones  or  general  storms  advance  .        .        .  125 
The  succession  of  winds  as  a  general  storm  passes  over  us    .  130 
The  way  a  particle  of  air  is  caused  to  take  a  contra-clock- 
wise spiral  in  entering  a  cyclone      .        ."...•        .        .  141 
Scheme  of  outflowing  winds  from  a  high        .        .        .     ~r  144 
Texan  norther  advancing  with  head  of  clouds       .        ...  150 

Low  with  extension  southward        .        .        .        ...  157 

The  winds  of  the  trouble  breeder    .        .        .        .    '    .        .  157 

Waterspouts ''  .  '  ;-.  159 

The  Lake  Gervais  (Minnesota)  tornado 161 

The  effects  of  an  ice  storm  in  Massachusetts  .        ,  -     .'        .  167 

Ranks  of  thunderstorms  gradually  deploying        .        ...  178 

Lightning .  v     .  184 

United  States  weather  map      .        .        .        .      - »      ' .'       .208 

Toy-balloon  barometer     .        .        .        .        .        fc        »        .  224 

Balance  barometer 225 

Mercurial  barometer 226 

Hair  hygrometer      .        .        .        ....        .        .        .  229 

Piche's  evaporimeter 231 


ABOUT  THE  WEATHER. 


CHAPTEK  I. 

CONTEST   OF   MANKIND    WITH   THE    WEATHEE. 

THE  world  outside  of  us,  which  we  call 
Nature,  may  be  looked  on  as  a  friend  that 
aids  us,  as  a  tutor  that  teaches  us  and  com- 
pels us  to  learn,  or  as  an  enemy  which  we  must 
conquer.  Each  point  of  view  is  a  true  one,  and 
each  has  its  interest  and  advantages.  Here  it 
suits  us  a  little  better  to  take  the  last  of  the 
three  standpoints,  and  look  on  the  long  prog- 
ress of  man  toward  the  highest  civilization  as  a 
series  of  struggles  with  the  great  elements  of 
Nature. 

These  elements  may,  if  not  controlled,  be 
destructive  to  him ;  may,  in  any  case,  tend  to 
limit  his  activity.  The  contests  with  them 
give  him,  if  he  is  strong,  greater  strength  and 
power — physical,  mental,  and  moral ;  but  weak- 
er individuals  and  races  go  to  the  wall  in  the 
long  fight. 


2  ABOUT  THE  WEATHER. 

The  struggle  can  be  divided  into  seven 
different  contests.  The  first  is  that  against 
the  inclemencies  of  weather  and  climate,  in 
which  man  sets  up  his  defenses  in  the  shape  of 
fixed  shelter  or  buildings,  and  portable  ones, 
or  garments.  This  contest,  and  the  weather 
against  which  it  is  made,  form  the  subject  of 
this  book,  and  later  will  be  discussed  in  full. 

The  second  contest  is  that  with  the  soil  and 
the  rocks,  and  its  success  means  agriculture  and 
mining.  It  is  the  first  decided  step  of  man 
above  the  beasts,  for  they,  as  well  as  he,  have 
to  fight  the  weather ;  but  they  do  not  attempt 
the  cultivation  of  the  earth,  nor  the  digging  up 
of  metals.  In  this  struggle  man  not  only  sub- 
dues the  soil,  but  selects  wild  plants,  and  by 
cultivation  and  care  makes  them  yield  him  a 
hundredfold  more  than  they  would  in  the  wild 
state.  Thus  he  subdues  wheat,  cotton,  the 
apple,  orange,  banana,  and  the  grape.  In  some 
cases,  as  the  banana,  the  plant  has  been  so 
changed  as  to  no  longer  even  produce  seed,  but 
depends  solely  on  man  for  its  continued  exist- 
ence on  the  earth. 

The  third  is  the  contest  of  animals ;  and  this 
means,  not  only  the  mastery  of  dangerous  wild 
animals,  but  the  conquest  of  several  kinds  by 
domestication,  whereby  they  become  the  friends 


CONTEST  OF  MANKIND  WITH  THE  WEATHER.        3 

and  slaves  of  man.  Some  have  been  so  com- 
pletely subdued  that  they  can  no  longer  sustain 
themselves  in  the  wild  state,  or  without  man's 
help.  They  have  also  been  so  changed  that  the 
ancestral  forms  in  most  cases  can  no  longer  be 
recognized.  This  is  the  step  that  more  than 
all  else  shows  man's  complete  mastery  of  the 
brutes.  In  the  end  the  most  of  the  species  of 
the  lower  animals  will  disappear. 

Fourth,  man's  conquest  of  the  forest  affords 
material  for  a  large  percentage  of  his  manu- 
factures. Fifth,  he  attempts  to  subdue  the 
forces  of  Nature,  and  having  made  an  obedient 
slave  of  that  powerful  and  heartless  monster, 
steam,  he  is  now  going  to  put  a  harness  on  the 
lightning,  making  it  replace  the  horse  on  the 
street  and  the  lamp  in  the  house. 

These,  by  the  establishment  of  routes  for 
the  use  of  travel,  commerce,  and  the  collection 
and  distribution  of  news,  make  the  great  task 
of  conquering  time  and  space  easier.  This 
sixth  is  one  of  the  greatest  of  man's  conquests 
over  Nature,  and  it  is  going  on  now  before 
our  very  eyes.  We  are  at  the  same  time  enter- 
ing upon  a  very  disagreeable  contest,  the  sev- 
enth, of  which  we  have  lately  learned  the  true 
character.  It  is  that  with  the  germs  of  dis- 
ease. The  diseases  we  have  known  for  ages, 


4  ABOUT  THE  WEATHER. 

but  we  have  only  lately  learned  what  makes 
them.  These  germs  of  disease  are  very  un- 
pleasant to  deal  with,  not  only  because  they  are 
the  causes  of  disease,  but  also  because  they  are 
creatures  of  filth.  They  are  also  creatures  of 
weather  and  climate,  and  must  be  referred  to 
from  time  to  time,  later.  Here  they  serve  to 
bring  us  back  to  the  weather,  which  is  our 
proper  topic,  and  from  which  we  strayed  to 
show  its  relations  to  other  things. 

The  greatest,  most  far-reaching,  and  most 
enduring  of  all  these  struggles  of  mankind  is 
that  with  the  weather.  It  begins  as  soon  as 
man  begins,  and  will  continue  as  long  as  man 
continues.  Man  constantly  succeeds  in  this 
contest,  and  as  constantly  finds  that  the  success 
in  the  last  battle  is  not  the  end  of  the  war. 

He  evades  the  rain  by  erecting  a  temporary 
or  permanent  roof,  or  he  escapes  the  cold  by 
taking  refuge  in  a  cave  or  building  a  fire.  But 
when  he  has  done  this  he  finds  the  work  still 
incomplete.  His  roof  is  not  yet  sufficiently 
perfect  to  meet  his  ever-new  demands,  and 
he  occupies  himself  for  centuries  in  im- 
proving it,  reaching  at  last  the  almost  per- 
fect form  of  overlapping  slates.  The  cave 
of  the  primeval  man  is  too  dark  or  too  open, 
his  fire  too  hot  or  too  cold.  Everything  needs 


CONTEST  OF   MANKIND   WITH   THE  WEATHER.        5 

adjustment,  and  again  new  adjustment,  to 
changed  conditions  or  to  changes  in  himself. 
And  when  he  has  obtained  shelter  for  himself 


FIG.  1.— An  Omaha  dwelling,  a  rude    protection  against    the 
weather. 

and  his  family,  he  must  have  it  for  his  animals, 
his  business,  also  his  commerce,  his  mails,  and 
so  on.  So  the  adjustment  goes — always  ad- 
vancing, never  quite  completed. 


ABOUT  THE  WEATHER. 


In  the  course  of  the  contest  man  finds  much 
to  compensate  him  for  the  labor  and  danger 
he  has  undergone.  The  first  result  is  his  dwell- 
ing (Fig.  1)  or  house,  and  to  this  is  due  all 


FIG.  2. — Japanese  cooly's  hat  and  straw  coat,  good  protectors 
against,  first  the  sun,  second  the  rain. 

those  domestic  and  legal  relations  which  good 
old-fashioned  English  sums  up  in  the  word 
"home."  From  these  relations,  we  are  told, 


CONTEST  OF   MANKIND   WITH  THE   WEATHER.        7 

are  derived  the  fundamental  principles  of 
society  (Fig.  2). 

Another  result  of  the  weather  contest  and 
the  creation  of  the  dwelling  is  that  great 
concentration  of  mankind,  that  enormous  ag- 
gregation of  men,  which  we  call  a  city.  An 
ordinary  tenement  house  has  the  population 
of  the  ordinary  small  village  or  hamlet,  and 
one  of  the  modern  lofty  office  buildings  has 
a  daytime  population  still  greater.  These 
things  are  possible  only  when  the  shelter  con- 
test has  created  an  advance  toward  perfect 
dwellings. 

The  mechanic  arts  receive  their  chief  stimu- 
lus from  the  necessity  of  protection  against  the 
weather.  They  are  fully  involved  in  the  struc- 
ture of  dwellings,  and  in  providing  all  those 
innumerable  requirements  of  our  civilization, 
such  as  sewers,  light,  heat,  and  water.  Con- 
venience, comfort,  and  luxury  must  be  equally 
consulted,  and  the  mechanic  arts  are  the  serv- 
ants of  each. 

To  this  struggle,  too,  belongs  the  develop- 
ment of  the  fine  arts.  All  these  require  pro- 
tection from  the  weather  except  landscape  gar- 
dening and,  to  a  less  degree,  sculpture  and 
architecture.  Books  and  leisure,  and  hence 
learning,  are  indebted  to  this  contest,  and  so 


8  ABOUT  THE  WEATHER. 

are  the  majority  of  the  refinements,  delicacies, 
and  elegances  of  life. 

But  the  chief  advantage  in  the  long  strug- 
gle is  not  so  much  in  what  man  has  done  as  in 
what  it  has  made  of  him.  The  fight  has  given 
him  a  high  degree  of  training,  and  developed 
the  brighter  and  more  success-compelling  side 
of  his  character,  giving  courage,  confidence,  self- 
reliance,  and  industry — a  most  worthy  quartette, 
all  of  the  highest  value.  The  moral  training 
that  comes  from  this  conquest  is  also  great,  for 
as  a  result  of  satisfying  his  social  instincts  in 
living  together  in  communities,  man  becomes, 
and  must  continue  to  be,  honest,  to  be  safe, 
honorable  to  be  respected,  forgiving  to  be  for- 
given, and  mild  if  his  life  is  to  be  peaceful  or 
even  tolerable. 


CHAPTEK  II. 

THE    WEATHER    CONQUEST   NOT   AN   UNMIXED 
BENEFIT. 

THE  protection  of  man  from  the  weather, 
like  all  other  conquests  and  successes,  is  made 
only  at  some  cost,  and  is  not  without  its  draw- 
backs. It  is  important  that  the  true  nature  of 
these  should  be  understood.  They  are  of  five 
different  kinds. 

The  first  is  the  artificial  sensitiveness  or 
lack  of  tone  which  is  introduced  by  the  civil- 
ized habit  of  carefully  protecting  one's  self. 
The  savage  is  free  from  this.  The  natives  of 
Tierra  del  Fuego  endure  a  climate  something 
like  that  of  Sitka  or  Juneau,  yet  live  in  boats 
or  imperfectly  constructed  huts,  and  have  only 
very  scanty  clothing,  often  nothing  more  than 
the  skin  of  some  wild  animal  about  the  loins. 
To  them  a  change  of  temperature,  that  would 
be  very  trying  to  us,  is  not  serious,  and  they 
suffer  only  in  extreme  weather.  Exposure  to 
the  weather  during  their  entire  lives  has  taken 


10  ABOUT  THE   WEATHER. 

away  the  sensitiveness  which  we,  for  many  suc- 
cessive generations,  have  cultivated. 

The  same  thing  is  shown  to  a  degree  by 
the  hand  and  foot.  We  accustom  the  hand  to 
remain  generally  uncovered,  while  the  foot  is 
kept  clothed.  The  result  is  that  the  hand  will 
bear  without  inconvenience  an  exposure  that 
to  the  foot  causes  suffering. 

The  protection  our  houses  and  garments 
afford  us  is  often  more  than  sufficient.  We 
can  live,  for  instance,  in  perfect  comfort  in  a 
house  kept  heated  to  60°  in  winter,  but  many 
tenants  heat  their  houses  to  70°  or  even  higher. 
The  latter  become  highly  sensitive  to  the  cold 
and  suffer  more  when  they  go  out  into  the 
open  air. 

The  remedy  lies  in  accustoming  one's  self  to 
living  in  cool  rooms,  to  wearing  light  clothing, 
and  especially  to  having  light  bedclothing. 
This  sensitiveness  and  lack  of  tone  are  proba- 
bly acquired  in  the  bed  chamber  more  than  else- 
where. Light  bedclothing  and  open  windows 
in  the  sleeping  room  will  go  far  toward  remedy- 
ing the  trouble,  and  will,  besides,  give  the  fresh- 
ness of  mind  and  body  which  results  in  cheer- 
fulness, and  in  clearness  of  skin  which  is  a  great 
part  of  beauty. 

When  this  sensitiveness  is  excessive  it  re- 


THE   WEATHER   CONQUEST.  H 

suits  in  a  series  of  dangerous  diseases.  Though 
comfortable  and  protected  at  home,  we  have  to 
go  out  into  the  open  air  from  time  to  time,  and 
when  the  weather  is  bad,  whether  very  hot  or 
very  cold,  very  wet  or  very  dry,  the  sudden  new 
and  sharp  impression  on  the  skin  may  have 
serious  consequences. 

The  least  dangerous  result  is  what  we  call 
a  cold.  The  blood  driven  suddenly  away  from 
the  surface  by  cold  or  damp  is  likely  to  accu- 
mulate in  too  great  a  degree  on  the  mucous 
surfaces  inside  the  body,  and  an  inflammation 
ensues.  If  this  goes  on  it  may  lead  to  pneu- 
monia, pleurisy,  or  some  similar  disease,  with 
great  and  immediate  danger  to  life,  or  it  may 
so  weaken  and  undermine  the  tone  of  the  mu- 
cous surfaces  that  they  easily  contract  other 
diseases. 

The  remedy  is  the  same  as  in  the  previous 
case.  It  is  necessary  for  those  who  wish  to  be 
vigorous  and  healthy  to  avoid  coddling ;  that 
should  be  left  to  genuine  invalids,  and  they 
should  have  as  little  of  it  as  possible. 

A  second  result  of  our  seclusion  from  the 
weather  is  neglect  of  physical  activity.  The 
pursuits  of  modern  society  run  to  the  intel- 
lectual and  neglect  the  physical  side  of  our 
nature.  The  result  is  the  loss  of  physical 


12  ABOUT  THE  WEATHER. 

strength  and  a  general  laxity  of  the  body,  caus- 
ing muscular  weakness,  besides  giving  rise  to 
obesity  greatly  injuring  physical  beauty. 

This  has  grown  so  serious  that  recently  a 
reform — modern  gymnastics — has  been  intro- 
duced to  correct  the  evil.  The  ancient  Greeks 
practiced  gymnastics  mainly  for  beauty,  and 
the  ancient  Romans  for  strength.  They  lived 
much  more  in  the  open  air  than  we  do.  We 
have  introduced  gymnastics  chiefly  to  remedy 
the  bad  results  of  too  much  confinement,  but 
even  with  the  limited  use  we  make  of  sys- 
tematic exercise  the  effect  in  increase  of  beauty 
and  strength  is  noteworthy. 

The  third  result  of  man's  protection  from 
the  weather  is  the  accumulation  about  him  of 
the  poisonous  products  of  his  own  life.  What- 
ever a  living  body  rejects  because  it  is  through 
with  it,  is  poison  if  taken  into  the  body  again. 
In  natural  surroundings  these  things  are  scat- 
tered and  diffused  until  they  are  innocuous,  but 
in  the  compact  and  closed  space  of  a  modern 
dwelling  they  are  as  much  prevented  from  being 
dissipated  as  is  the  heat ;  and  this  state  of 
things  is  still  worse  in  a  city  where  the 
dwellings  themselves  are  crowded — so  crowded 
that  a  single  building  may  contain  many  different 
dwellings,  each  occupied  by  a  separate  family. 


THE  WEATHER  CONQUEST.  13 

Now,  the  accumulation  of  poison  most 
likely  to  occur  is  that  of  carbonic-acid  gas,  for 
it  is  not  only  given  off  by  the  breath,  but  also 
by  the  fires  and  the  flames  of  the  candle,  lamp, 
and  gas  jet.  And  this  gas  is  still  more  likely  to 
accumulate  in  public  halls  where  many  people 
come  together.  It  suffocates  by  cutting  off 
the  supply  of  wholesome  air,  and  it  also 
poisons ;  when  abundant,  it  proves  fatal  in  a 
few  hours. 

The  poisonous  gas  next  most  likely  to  ac- 
cumulate is  that  from  the  sewers  in  a  city.  It 
is  an  indirect  product  of  all  the  excretions  and 
other  substances,  mainly  products  of  decay, 
carried  off  by  the  sewers,  and  is  so  lacking  in 
odor  that  it  can  not  be  recognized  by  its  smell. 
It  is  sure  to  come  into  a  city  house  which  has 
been  unoccupied,  where  the  traps  have  been 
neglected.  It  is  more  poisonous  than  carbonic- 
acid  gas. 

The  remedy  for  these  dangers,  due  to  the 
very  completeness  of  modern  dwellings,  is  in 
ventilation ;  but  this  is  the  one  feature  of  our 
buildings  which  has  not  yet  been  perfected  to 
a  point  of  genuine  safety.  Ventilation  is  diffi- 
cult to  manage  in  winter  without  great  loss  of 
heat  and  expense  in  fuel.  The  best  ventilator 
of  all  is  an  open  fireplace,  but  it  is  the  very 


14  ABOUT  THE  WEATHER. 

form  of  heating  which  is  most  wasteful  and 
extravagant. 

The  fourth  and  worst  result  of  protection 
from  the  weather  is  the  opportunity  it  gives 
for  the  development  of  seeds  of  deadly  diseases. 
In  a  natural  condition  these  seeds  or  germs  are 
developed  in  relatively  small  numbers,  have 
little  strength  to  injure,  and  are  so  blown 
about  by  the  wind  that  they  do  little  damage. 
Moreover,  the  rays  of  the  sun  usually  destroy 
them ;  and  in  the  open  air  under  the  sky  they 
find  few  secure  places  of  refuge.  They  are, 
when  exposed  to  the  open  air,  dangerous  only 
in  the  heat  of  the  tropics  and  in  certain  damp, 
dark,  and  swampy  places  in  the  temperate 
zones. 

These  little  invisible  fragments  of  life  are 
especially  fond  of  filth,  where  they  grow^  much 
better  than  in  clean  places.  When  they  find  filth, 
heat,  and  darkness  all  together,  they  multiply 
at  an  amazing  rate,  and  at  the  same  time  be- 
come malignant.  All  these  they  find  in  cer- 
tain tropical  cities,  as  Canton  and  Bombay, 
and  there  they  sometimes  become  so  deadly 
that  the  very  rats,  that  usually  live  and  thrive 
on  filth,  sicken  and  die  in  great  numbers. 

Such  conditions  sometimes  occur  in  neg- 
lected spots  in  all  cities  and  in  unclean  houses, 


THE  WEATHER  CONQUEST.  15 

and  these  may  become  centers  from  which  pour 
out  multitudes  of  the  minute,  death-carrying 
germs.  The  only  remedy  is  cleanliness  ;  and 
cleanliness  on  a  large  scale  is  called  sanitation. 
The  sanitary  officers  of  a  great  city,  in  insisting 
on  a  high  degree  of  cleanliness  everywhere,  do  an 
amount  of  good  which  can  hardly  be  overesti- 
mated. 

,  When  germs  of  disease  have  found  a  suitable 
home  and  have  begun  to  spread,  they  may  be 
carried  about  in  the  clothing  or  in  the  bag- 
gage of  travelers,  and  especially  in  the  bodies  of 
those  already  diseased.  Then  another  remedy 
has  to  be  set  up  ;  for  it  is  not  only  necessary  to 
be  clean  one's  self,  but  to  avoid  contamination 
by  others.  It  is  curious  to  think  of  men  patrol- 
ing  the  boundary  of  a  country  with  guns  in 
their  hands  to  keep  out  an  army  of  minute,  in- 
visible germs ;  but  this  is  often  successfully  done. 
The  last  of  the  drawbacks  to  our  conquest 
of  the  weather  to  which  we  shall  refer,  is  per- 
haps the  most  painful  of  all.  In  his  conquest 
man  has  developed  luxury,  and  made  a  large 
number  of  needless  things  absolutely  necessary 
and  indispensable.  To  a  savage  the  number  of 
things  which  he  must  have  probably  does  not 
number  twenty,  and  to  the  Tierra  del  Fuegian 
or  the  black  fellow  of  Australia  may  not  num- 


16  ABOUT  THE  WEATHER. 

ber  half  a  dozen.  To  the  writer  of  this  they 
number  at  least  five  hundred,  and  to  the  reader 
perhaps  more.  Let  him  count  them  and  see. 
An  Indian  travels  with  almost  nothing  except 
his  horse,  garments,  and  weapons ;  a  modern 
belle  travels  with  huge  trunkf  uls,  and  these  are 
all  necessities  to  her. 

The  development  of  the  needs  of  modern 
life,  due  largely  to  the  weather  conquest,  has 
made  more  money  necessary,  and  this  makes 
poverty  more  difficult  to  avoid  and  more  com- 
mon. What  feeds  an  Arab  abundantly  is  starv- 
ing provision  for  one  of  us.  The  pressure  of 
poverty  causes  not  only  unhappiness,  but  is  a 
fertile  source  of  crime.  The  remedies  for  pov- 
erty and  crime  are  found  in  philanthropy  and 
law.  They  are  not  at  all  to  be  sought  for  in 
the  idea  of  some  visionaries,  that  we  may  return 
to  the  simplicity  of  the  savage. 

Man  has  become  civilized  to  stay  civilized, 
and  to  grow  more  so.  The  burdens  of  needs 
which  civilization  causes  can  not  be  laid  down, 
but  will  grow.  The  readjustment  is  not  in  go- 
ing into  the  woods  and  living  in  a  cave,  but  in 
the  development  of  society,  and  chiefly  in  phi- 
lanthropy. Then  this  very  evil  brings  about  a 
good  in  that  it  gives  greater  opportunity  to  the 
generous  and  noble-minded. 


CHAPTEK  III. 

THE   INCOMPLETENESS    OF   THE   WEATHER 
CONQUEST. 

THE  struggle  with  the  weather  not  only  has 
its  bad  results,  but  it  is  still  incomplete.  No 
sooner  do  we  perfect  one  means  of  protection 
than  our  requirements  change  and  a  readjust- 
ment is  necessary.  A  protection  from  the  or- 
dinary weather  is  not  sufficient  for  the  extraor- 
dinary. Some  years  ago  a  prominent  Eastern 
engineer  was  called  to  a  new  Western  city  to 
devise  a  system  of  sewers.  "What  is  your 
largest  rainfall  per  hour  ? "  he  asked.  "  A  third 
of  an  inch,"  was  the  answer.  To  be  quite  safe, 
the  engineer  constructed  the  sewers  to  carry  off 
a  rainfall  twice  as  heavy.  But  hardly  were 
the  sewers  completed  when  still  heavier  rain- 
falls than  those  provided  for  occurred,  and  that 
city  has  still  to  submit  to  occasional  overflows 
of  the  streets  from  rainfalls  greater  than  those 
for  which  the  sewers  were  constructed.  Simi- 
lar miscalculations  are  sometimes  found  in  the 

17 


18  ABOUT  THE  WEATHER. 

plumbing  in  our  houses  and  in  many  other 
ways. 

Weather  for  which  we  are  not  prepared  is 
met  with  oftenest  by  persons  engaged  in  open- 
air  pursuits.  The  farmer  feels  this  with  espe- 
cial bitterness.  There  is  hardly  a  variation 
from  average  weather  which  is  not  injurious 
to  him,  for  nearly  all  that  he  has  lies  exposed 
to  the  weather.  Now  it  is  the  unexpected 
summer  shower  which  destroys  his  hay  ;  again, 
it  is  a  capful  of  wind  that  lays  down  his  best 
wheat  and  oats  until  it  so  increases  the  cost  of 
harvesting  that  his  profits  disappear ;  an  untime- 
ly frost,  or  drought,  or  rain,  or  snow,  or  wind 
may  destroy  a  large  part  of  his  season's  work. 

The  stock  grower  is  hardly  less  fortunate. 
In  the  geological  strata  of  the  Western  plains 
are  found  what  are  called  bone  beds — places 
where  there  are  enormous  accumulations  of 
fossil  bones.  From  them  geologists  have  been 
able  to  reconstruct  curious  animals  which  used 
to  live  there  in  numbers,  but  have  died  out 
ages  ago.  These  beds  are  where  the  animals 
were  huddled  together  and  killed  by  severe 
storms.  The  same  kinds  of  storms  still  occur 
there,  and  they  are  as  deadly,  but  now  it  is  the 
cattle,  horses,  and  sheep  of  the  stockman  that 
suffer. 


INCOMPLETENESS  OF  THE  WEATHER  CONQUEST.    19 

The  danger  to  sailors  of  severe  weather  is 
well  knowrn,  but  experience  proves  that  some 
forms  of  extreme  weather  are  nearly  as  danger- 
ous to  those  who  use  steam  as  to  those  who  use 
sails.  Probably  steam  navigation  is  the  safest 
way  of  traveling;  but  it  has  its  perils,  due 
to  heavy  winds  and  heavy  seas,  and  especially 
to  heavy  fogs. 

Still  more  sensitive  to  weather  changes  is 
the  art  of  transportation  by  land,  which  has 
had  such  enormous  development  almost  within 
the  memory  of  many  who  yet  live.  Since  1 805 
the  number  of  miles  of  railway  has  grown  from 
nothing  to  about  half  a  million  miles ;  enough 
to  make  a  double  steel  band  from  pole  to  pole 
forty  times  over,  and  to  give  employment  to 
perhaps  five  millions  of  people.  The  street- 
railway  development  is  later  and  even  more 
remarkable.  This  enormous  network  makes 
the  very  arteries  and  veins  of  the  world's  land 
business,  and  any  interruption  to  it  is  felt 
within  a  few  hours  in  every  home,  except  the 
most  isolated  or  the  savage  ones. 

This  modern  business  called  transportation 
is  especially  liable  to  injury  by  the  weather,  both 
because  it  is  carried  on  beneath  the  sky  and 
because,  being  new,  it  has  not  yet  completely 
adjusted  itself  to  the  conditions  under  which 


20  ABOUT  THE   WEATHER. 

it  exists.  Floods  carrying  away  its  bridges  and 
culverts,  interrupt  its  business;  heats  dry  up 
its  wooden  structures  and  lead  to  their  burn- 
ing ;  thaws  bring  avalanches  of  snow  and  earth 
on  its  track,  and  even  a  fall  of  snow  of  very 
moderate  character  may  delay,  or  for  a  time, 
interrupt  traffic. 

In  addition  to  all  this  there  is  always  a 
possible  series  of  injuries  to  its  freight  by 
frosts  or  unusual  heats.  Indeed,  it  is  not  easy 
to  protect  large  boxes  on  wheels,  flying  along 
at  twenty  miles  an  hour  or  more,  against  the 
weather. 

A  very  curious  modern  development  is  that 
of  trade  in  information,  for  commercial  and 
journalistic  purposes.  This  involves  the  wires 
and  poles  of  the  telegraph  and  telephone  com- 
panies, and  the  business  is  especially  sensitive 
to  the  weather.  Even  the  electric  condition, 
that  part  of  the  weather  which  is  most  ob- 
scure, is  here  of  great  importance. 

Another  of  the  great  interests  of  man  espe- 
cially subject  to  weather  changes,  though  in 
limited  directions,  is  the  system  of  streets  of  a 
great  city.  The  relation  of  the  rainfall  to  the 
sewers  has  already  been  mentioned.  The  rain 
also  produces  mud  on  the  street,  which  must 
be  removed  as  soon  as  possible ;  a  heavy  fall 


INCOMPLETENESS  OF  THE  WEATHER  CONQUEST.   21 

of  snow  calls  out  an  army  of  men  and  horses 
to  clear  away  this  great  obstruction  to  traffic. 
The  actual  care  of  the  streets  of  Boston  for  the 
first  fortnight  in  February,  1898,  cost  eighty- 
eight  thousand  dollars,  and  to  clean  the  snow 
from  all  the  streets  of  New  York  city  it  is  esti- 
mated would  take  two  millions  of  dollars  per 
year. 

These  figures  give  some  conception  of  the 
money  interests  involved.  The  remedies  em- 
ployed and  attempted  are  numerous  and  elabo- 
rate. They  will  be  noticed  in  the  succeeding 
chapters. 


CHAPTER  IV. 

REMEDIES    FOR    INJURIES    BY    WEATHER. 

REMEDIES  for  the  injuries  inflicted  upon  man 
by  extremes  of  weather  have  been  actively  and 
earnestly  sought  in  all  directions.  Attempts 
have  been  made  to  predict  the  weather  ac- 
curately, to  try  to  solve  the  complete  weather 
problem,  and  even  to  try  to  make  weather. 
The  remedies  are  undertakings  which,  when 
successful,  bring  a  great  compensation  with 
them.  The  person  who  invents  a  device  or 
discovers  a  way  to  save  the  railway  companies 
a  cent  a  mile  per  train,  or  the  farmer  a  cent  a 
month  per  acre,  will  be  rewarded  by  a  fortune. 

To  illustrate,  let  us  take  that  newest  of 
arts,  the  use  of  electricity.  It  suffers  from 
weather  exposure  in  many  ways.  The  poles 
and  wires  are  especially  liable  to  be  struck  by 
lightning  out  on  open  plains  or  when  crossing 
bare  mountains.  Sometimes  the  lightning 
spreads  along  the  wire  and  shatters  a  dozen  or 
a  score  of  posts  on  either  side  of  the  road. 

22 


REMEDIES   FOR  INJURIES  BY  WEATHER.       23 

The  apparatus  for  conducting  man's  tamed 
lightning  needs  especial  protection  from  the 
wild  lightning  of  Nature,  and  a  series  of 
special  lightning  conductors  and  lightning 
arresters  have  been  devised. 

In  some  cases  the  lightning  is  taken  up  with- 
out  discharge  by  the  wires  and  conducted  to 
the  receiving  instruments  in  the  offices,  where 
it  may  only  glow  and  supply  a  surplus  which 
replaces  the  comparatively  feeble  currents  made 
by  man,  and  in  this  way  interrupt  business ;  or 
it  may  make  discharges  which,  are  dangerous 
to  the  operators,  or  which  burn  out  the  instru- 
ments, and  perhaps  set  fire  to  the  building. 
The  danger  at  the  receiving  instruments  is 
repeated  wherever  there  is  a  break  or  a  weak 
point  in  the  wires.  To  remedy  these  dangers, 
lightning  arresters  and  other  devices  are  used ; 
they  are  only  partially  effective. 

If  the  state  of  the  atmosphere  is  foggy  or 
rainy,  or  even  very  moist,  the  insulation  be- 
comes incomplete,  and  the  electric  current  leaks 
away  to  the  ground,  causing  interruption  of 
business  and  danger  to  life  and  property  where 
the  leakage  occurs.  Special  devices  for  insula- 
tion are  required  to  avoid  this,  and  they  are  of 
varied  character.  These  are  all  cases  of  over- 
charge or  loss  to  the  current. 


24  ABOUT  THE    WEATHER. 

Another  series  of  weather  extremes  brings 
the  wires  to  the  ground.     For  instance,  in  cer- 


FIG.  3. — Accumulation  of  hoarfrost  on  Mount  Washington  in 
winter. 

(From  a  photograph  published  by  Kilburn  and  Company,  Littleton,  N.  H. 
Loaned  by  the  Weather  Bureau.) 

tain  exposed  situations,  as  in  mountain  passes, 
hoarfrost   forms   to  an  enormous  amount,  be- 


UEMEDIE3  FOE   INJURIES  BY   WEATHER.       25 

coming  sometimes  a  foot  thick  on  all  stationary 
objects.  This  breaks  down  the  wires.  Ice 
storms  load  the  wires  with  a  similar  result. 
No  satisfactory  remedy  for  these  dangers  has 
been  found.  They  are  not  common,  but,  so  far, 
admit  of  no  remedy.  They  can  be  repaired 
only  after  the  damage  has  been  done. 

There  is  also  a  series  of  damages  to  which 
the  poles  are  exposed.  Lightning  may  shatter 
them ;  floods  may  carry  them  away  ;  landslides 
may  overwhelm  them,  and  snow  slides  among 
mountains  are  quite  as  damaging  in  the  spring 
or  during  warm  storms.  To  remedy  these  dan- 
gers, wires  have  been  put  underground,  but 
there  a  new  series  of  leakages  and  breaks 
occur,  and  it  is  difficult  to  get  at  the  wires  to 
remedy  accidents. 

These  details  have  been  given  at  some  length 
to  illustrate  how  dependent  upon  the  weather 
and  how  subject  to  damage  by  it,  is  the  prac- 
tice of  that  new  art,  applied  electricity.  There 
are  also  many  injuries  to  which  the  practice  of 
modern  arts  and  industries,  carried  on  in  the 
open  air,  are  subject,  for  which  no  complete 
remedy  has  yet  been  found. 

The  air,  soft  as  it  is,  offers  resistance  to 
anything  moving  in  it.  This  resistance,  when 
the  motion  is  slow,  is  very  slight,  and  we  hardly 


26  ABOUT  THE  WEATHER. 

feel  it  when  walking;  if  we  run  it  becomes 
noticeable,  and  in  rapid  motion  on  a  bicycle  it 
is  the  most  serious  difficulty  to  overcome. 

Calculation  and  experiment  have  shown 
that  to  anything  moving  at  the  rate  of  twenty 
miles  an  hour — and  this  is  a  common  rate  of 
speed  on  railway  trains,  and  not  very  hard  to 
reach  on  bicycles — the  air  offers  a  resistance  of 
two  pounds  avoirdupois  to  every  square  foot 
of  surface  exposed  to  it ;  that  is,  it  takes  a 
push  of  two  pounds  to  every  square  foot  to 
force  the  air  out  of  the  way  when  we  are 
moving  at  the  rate  of  twenty  miles  an  hour. 
This  resistance  increases  rapidly  as  the  speed 
increases  ;  in  fact,  as  the  square  of  the  velocity. 
If  the  rate  is  forty  miles  (two  times  the  first  men- 
tioned), the  resistance  is  four  times  that  of  the 
first  instance,  or  eight  pounds  to  the  square  foot ; 
and  if  it  is  sixty  (tliree  times  twenty)  miles  per 
hour,  the  resistance  is  nine  times  two  pounds,  or 
eighteen  pounds,  per  square  foot.  If  a  train 
moves  at  the  rate  of  a  hundred  miles  an  hour, 
as  they  promise  it  shall  on  certain  new  forms  of 
electric  railways  made  especially  for  speed,  the 
pressure  will  be  fifty  pounds  per  square  foot. 

The  adult  human  body,  taking  clothing 
into  account,  presents  a  front  surface  of  about 
five  square  feet ;  were  it  not  that  it  is  rounded 


REMEDIES  FOR  INJURIES  BY  WEATHER.       27 

and  that  eddies  occur  behind  it,  it  would  have 
to  support  a  pressure  of  ninety  pounds  when 
carried  in  an  erect  posture — for  instance, 
on  a  flat  car  at  sixty  miles  an  hour.  An  or- 
dinary train  has  a  frontage  of  several  hun- 
dred square  feet  directed  forward  against  the 
air,  and  but  for  the  eddies  it  would  have  to 
add  enormously  to  its  pull  to  overcome  the 
resistance  of  the  atmosphere  through  which  it 
moves.  As  it  is,  the  power  required  to  push 
against  the  air  soon  becomes  equal  to  that 
needed  to  take  the  train  forward.  Probably 
this  occurs  at  a  speed  of  about  fifty  miles  an 
hour. 

The  resistance  is  lessened  when  the  pres- 
sure decreases,  as  when  a  low-pressure  storm 
is  coming  on,  or  when  the  train  is  at  high  alti- 
tudes, but  the  resistance  of  the  still  air  to  a 
train  moving  through  it  is  the  same  as  that 
offered  by  a  wind  moving  against  it.  A  high 
head- wind  causes  a  great  increase  of  work  to  a 
locomotive,  and  thus  a  great  loss  of  fuel. 

This  could  be  remedied  in  part  by  chang- 
ing the  form  of  the  surfaces  of  the  train  that 
are  directed  forward.  The  locomotive  should 
be  so  made  as  to  split  the  air.  The  only  im- 
provement thus  far  introduced  is  the  vestibule 
between  passenger  coaches.  This  takes  away 
4 


28 


ABOUT  THE  WEATHER. 


REMEDIES   FOR   INJURIES   BY   WEATHER.       29 

the  pressure  on  the  heads  of  the  individual 
coaches,  except  the  forward  one,  and  so  greatly 
decreases  the  resistance. 

Another  illustration  of  modern  remedies 
against  the  weather  is  to  be  found  in  the  de- 
vices to  prevent  snow  from  falling  on  railway 
tracks,  or  to  remove  it  when  it  has  once  fallen. 
Sometimes  the  track  is  covered  with  great  un- 
sightly sheds,  miles  long,  especially  in  mountain 
regions  where  the  snow  is  likely  to  be  very 
deep.  On  open  places,  over  which  the  wind 
has  a  great  sweep,  snow  fences  are  erected  in 
such  a  way  as  to  take  advantage  of  the  eddies 
and  make  the  wind  itself  keep  the  track  clear. 

When  neither  of  these  is  practicable,  snow- 
plows  placed  in  front  of  a  locomotive  are  used. 
Plunging  through  the  snow  at  a  high  rate  of 
speed,  they  throw  it,  when  light,  far  away  on 
each  side.  Snow  brooms,  used  for  the  same 
purpose  on  street-car  lines,  have  to  be  kept 
running  during  the  entire  storm.  When  the 
snow  is  heavy  and  wet  and  packs,  and  espe- 
cially when  it  freezes,  the  road  may  be  blocked 
until  an  army  of  men  has  been  set  to  work 
to  clear  it  away,  and  they  may  have  to  work 
at  it  with  pick  and  blast  as  if  it  were  so  much 
rock. 

Fogs,  which  cause  such  a  dangerous  delay 


30  ABOUT  THE  WEATHER. 

to  shipping,  are  remedied  to  some  degree  by 
fog  bells  or  fog  horns,  but  the  sounds  from 
these  instruments  do  not  reach  far,  and  they 
also  are  curiously  ineffective  in  spots  even 
within  the  area  where  the  sound  ought  to  reach. 
There  are  places  of  sound  shadow,  due  some- 
times to  rocks  and  islands,  and  sometimes  to 
other  causes  not  yet  known.  There  are  patches 
within  easy  reach  of  the  bell  or  horn  where 
no  sound  can  be  heard,  and  these,  it  appears, 
may  be  differently  located  at  different  times. 
These  areas  of  silence  seem  to  be  due  to  the 
fog  itself,  and  they  are  especially  dangerous, 
for  the  seaman  naturally  thinks  that  if  he  does 
not  hear  the  sound  it  is  because  he  is  too  far 
away.  A  remedy  for  fog  will  probably  be 
found  in  the  telephone,  for  it  has  been  proved 
that  the  water  itself  may  take  the  place  of  a 
wire  in  conveying  sounds. 

Artificial  weather  is  made  in  our  houses  and 
other  buildings,  and  especially  in  hot -houses 
and  refrigerators,  and  the  attempt  has  been 
made  to  produce  rain  by  artificial  means.  The 
best  -  known  instance  of  this  is  that  of  Mr. 
Dyrenforth,  who  experimented  with  explosions 
for  the  purpose,  with  money  furnished  by  Con- 
gress. He  carried  on  his  observations  near 
Washington  city  and  in  Texas,  but  was  not 


REMEDIES   FOR  INJURIES    BY  WEATHER.       31 

able  to  make  rain.  It  is  difficult  enough,  and 
expensive  enough,  to  make  better  weather  in 
our  dwellings,  without  attempting  to  make  it 
for  all  outdoors.  No  one  has  yet  proved  that 
explosions  will  bring  rain ;  but  if  that  were 
proved,  it  can  hardly  be  believed  that  man's 
puny  cannon,  whose  sound,  even,  reaches  but 
a  few  miles,  could  cause  rain  over  a  State,  or 
even  over  a  county. 

The  best  and  most  complete  precaution 
against  the  weather  can  be  found  in  predicting 
it  beforehand,  thus  forewarning  those  likely  to 
suffer  from  it.  This  has  been  done  in  various 
ways  and  with  varying  success.  Prediction 
by  weather  signs  is  successful  in  experienced 
hands  for  at  least  a  few  hours  ahead.  The 
barometer  is  the  best  guide  that  has  been  dis- 
covered for  such  predictions,  and  the  clouds 
next  best.  The  weather  map  is  a  great  im- 
provement on  the  tabular  reports,  for  it  pre- 
sents a  view  of  the  weather  for  the  same  mo- 
ment over  an  entire  country,  and  so  permits 
prediction  for  a  day  or  two  ahead.  This  is 
the  method  used  by  the  Weather  Bureau.  At- 
tempts have  been  made  by  special  methods  to 
extend  the  predictions  to  a  much  longer  time 
ahead — for  a  month,  a  season,  or  longer — but 
these  promise  little  success. 


32  ABOUT  THE  WEATHER. 

We  shall  show  the  weather-map  method  at 
some  length,  but  first  we  shall  have  to  know 
about  the  elements  of  the  weather  and  their 
combinations  into  storms,  and  modifications  by 
the  season  and  the  lay  of  the  land.  The  suc- 
ceeding chapters  will  be  devoted  to  these  sub- 
jects. 

The  late  development  of  wireless  telegraphy 
promises  to  be  the  most  efficient  aid  yet  dis- 
covered to  weather  prediction. 

Electric  waves  have  been  known  experi- 
mentally since  1886,  but  their  use  in  sending 
messages  is  much  more  recent.  Apparatus  has 
been  devised  for  developing  these  waves  in 
great  intensity,  so  that  they  can  be  made  effi- 
cient in  carrying  messages  for  distances  as  great 
as  twenty  miles,  and  perhaps  much  more. 

By  the  use  of  fixed  signal  stations  perfect 
communication  can  be  maintained  with  parts 
of  the  earth  and  ocean  where  the  use  of  wires  is 
not  practicable ;  and  as  neither  fog  nor  storm 
nor  masses  of  earth  or  rock  interfere  materially 
with  the  electrical  impulses,  it  is  evident  that 
no  more  perfect  method  of  sending  weather  re- 
ports can  well  be  imagined. 


CHAPTER  Y. 

THE   PRESSURE   OF   THE   AIR   AND   HOW    IT   IS 
MEASURED. 

LIKE  all  material  things  on  the  earth,  the  air 
has  weight,  which,  though  small,  is  apprecia- 
ble. It  takes  seven  or  eight  hundred  gallons  of 
it  to  balance  one  gallon  of  water.  It  is  lighter 
when  warm,  for,  like  other  things,  it  expands 
with  increase  in  temperature.  It  is  also  lighter 
when  moist,  for  a  given  amount  of  the  vapor  of 
water  weighs  but  little  more  than  half  as  much 
as  an  equal  quantity  of  dry  air.  Air  also  de- 
creases in  weight  in  ratio  of  its  release  from 
pressure,  as  when  in  an  air  pump  or  in  the 
upper  regions  of  the  atmosphere. 

In  ordinary  weather  the  weight  of  a  cubic 
foot  of  air  is  from  five  hundred  to  six  hundred 
grains,  the  lesser  value  when  the  temperature 
is  higher.  In  an  ordinary  room,  heated  to  sev- 
enty degrees  and  kept  moist,  the  weight  of  the 
inclosed  air  is  five  hundred  and  twenty  grains 
to  each  cubic  foot.  In  a  room  twenty  feet 


34  ABOUT  THE  WEATHER. 

square  and  ten  feet  high  this  gives  a  total 
weight  of  two  hundred  and  ninety-seven  pounds 
avoirdupois  for  the  air — equal  to  thirty-seven 
gallons,  or  fourteen  pailfuls  of  water,  or  nearly 
three  gallons  of  mercury.  The  weight  is  di- 
vided among  the  gases  of  the  air  very  un- 
equally. There  would  be  in  this  room  of 
twenty  feet  square  two  hundred  and  thirty- 
one  pounds  of  nitrogen,  sixty-one  of  oxygen, 
and  four  pounds  of  the  vapor  of  water.  The 
last  when  condensed  makes  two  quarts  of 
water. 

The  pressure  from  anything  depends  on 
its  weight  and  the  mobility  of  its  particles. 
In  the  case  of  solids  it  is  only  the  pressure  down- 
ward that  wTe  feel,  but  in  a  liquid  or  gas  the 
pressure  is  exerted  equally  in  every  direction. 
A  gas,  like  the  air,  creeps  through  the  finest  crev- 
ices, and  wherever  it  goes  it  takes  the  pressure 
wTith  it.  It  passes  through  holes  so  small  that 
it  is  not  easy  to  make  anything  air-tight,  and 
the  full  pressure  of  the  air  is  conveyed  through 
a  keyhole  or  through  a  pinhole  as  effectively 
as  in  the  open  air  under  the  sky. 

We  are  at  the  bottom  of  the  ocean  of  air, 
and  so  get  the  weight  of  all  of  it  that  is  di- 
rectly above  us.  The  air  is  several  hundred 
miles  deep,  and  a  column  of  this  length  is  press- 


THE  PRESSURE  OP  THE  AIR.  35 

ing  upon  us,  pressing  not  only  downwards  but 
at  the  sides  and  upwards.  Although  the  air 
is  light  in  itself  this  is  enough  to  give  a  heavy 
weight.  It  is  measured  by  making  it  balance  a 
weight  in  vacuum,  and  this  is  most  easily  done 
with  the  mercurial  barometer  when  a  closed 
glass  tube  preserves  a  vacuum  above  the  mer- 
cury. 

In  this  way  it  is  found  that  the  pressure  of 
the  air  at  sea-level  is  nearly  fifteen  pounds  on 
each  square  inch.  This  means  that  on  each 
square  inch  of  everything — the  floor,  the  walls, 
the  ceiling,  an  eggshell,  a  glass  bottle,  the  sur- 
face of  animals  and  plants,  however  delicate 
they  may  be — there  is  a  pressure  equal  to  the 
weight  of  a  gallon  and  a  half  of  water  or  that 
of  a  peck  of  wheat.  On  each  square  foot  the 
pressure  is  more  than  a  ton  !  On  the  floor  of 
the  room  twenty  feet  square,  mentioned  above, 
there  is  an  air  pressure  of  400  tons,  on  the  ceil- 
ing the  same,  and  800  tons  on  the  walls,  mak- 
ing 1,600  tons  in  all,  or,  to  be  exact,  1,728. 

The  natural  question  arises,  why  all  things, 
except  the  most  solid  ones,  are  not  crushed  by 
this  enormous  pressure  ?  They  would  be  were 
it  not  for  the  fact  that  the  pressure  is  equal  on 
all  sides.  The  pressure  downward  upon  the 
floor  is  counterbalanced  by  an  equal  pressure 


36  ABOUT  THE  WEATHER. 

upward,  and  that  upward  upon  the  ceiling  by 
an  equal  one  downward.  If  the  air  is  removed 
from  one  side  this  pressure  very  plainly  mani- 
fests itself.  For  instance,  in  the  old-fashioned 
way  of  bleeding  people  a  process  called  cup- 
ping was  used,  which  made  the  pressure  of  the 
air  aid  in  causing  a  flow  of 
the  blood.  A  bit  of  paper 
was  set  fire  to,  placed  in  a 
little  glass  beaker,  and  this 
was  clapped  on  the  fleshy 
part  of  the  arm  and  pressed 
down.  The  paper  burned 
.  for  a  moment  without  in- 

/  jury  to  the  patient,  and  in 

FIG.   5.— illustration   of  burning  used  up  a  part  of 

the  suction   effect    of    ,-•          .          m-i          •  j        ji 

air   pressure  in   the  the  air.     The  air  under  the 

old-fashioned  cupping   hprjVpr    Woq   fhpri    IPQQ    fhan 
practiced  by  doctors. 

that  on  the  outside,  and 
the  pressure  forced,  or  the  suction  drew,  the 
flesh  up  into  the  glass  dish,  and  the  blood  out 
of  the  little  wound  which  the  physician  had 
made  in  it.  Indeed,  all  suction  depends  on  this 
pressure  of  the  air.  When  a  pump  works  it 
draws  out  the  air  which  is  prevented  from  re- 
turning by  the  valves.  The  column  of  water  is 
then  forced  up  into  the  pump  by  the  pressure  of 
the  air  on  the  surface  of  water  supply  below. 


THE  PRESSURE  OF  THE  AIR 


37 


The  pressure  of  the  air  can  be  seen  at  work 
in  a  great  many  ways.  The  suction  pump  just- 
mentioned  calls  it  into  action.  The  pressure  of 
the  air  is  enough 
to  balance  a  col- 
umn of  water 
thirty-four  feet 
high,  and  a  suc- 
tion pump  will 
work  to  this 
height  and  no 
higher.  The  si- 
phon and  the  air- 
brakes of  the 
railway  coaches 
also  use  the  pres- 
sure of  the  air. 

The  air  is 
pumped  out 
from  a  series  of 
tubes  in  the  en- 
gine so  arranged 
that  this  air  will 


FIG.  6, — Pump. 


then  operate  to  press  the  brake  shoes  against 
the  car  wheels. 

A  very  pretty  experiment  can  be  used  to 
show  air  pressure.  Fill  a  tumbler  evenly  full 
of  water,  and  then  press  over  the  top  a  square 


-: 

(   UNJVF.pl' 


38  ABOUT  THE  WEATHER. 

of  writing  or  blotting  paper.  Press  the  latter 
down  lightly,  but  evenly,  until  it  is  in  close 
contact  with  the  surface 
of  water  and  the  edge  of 
the  tumbler.  Then  plac- 
ing the  palm  of  your  hand 
over  the  top  of  the  glass, 
reverse  quickly,  take  away 
your  hand,  and  the  air 
pressing  on  the  paper  will 
keep  the  water  in  the 
FIG.  ?.— illustration  of  air  tumbler.  The  paper  pre- 

pressure  upwards.     In-  ,  ••_        •      »  i  . 

verted  tumbler  of  water  vents  the  air  from  rushing 

kept  from  emptying  by    •        j.       j.   -L       J.-L       WUpp     nf 
a  piece  of  paper. 

the  water. 

Air  pressure  is  most  easily  measured  by  a 
mercurial  barometer.  This  is  a  column  of  mer- 
cury in  a  glass  tube  closed  above  but  opening 
below  in  a  small  basin  of  mercury.  The  col- 
umn is  supported  by  the  pressure  of  the  air  on 
the  surface  of  mercury  in  the  basin.  Observa- 
tions are  made  by  measuring  the  distance  be- 
tween the  surface  of  the  mercury  and  the  top 
of  the  tube.  At  sea  level  the  height  is  about 
thirty  inches.  The  mercury  changes  its  dimen- 
sions a  little  with  changes  in  temperature,  and 
for  this  a  small  correction  must  be  made. 

Any  liquid  can  be  used  in  making  a  barom- 


THE  PRESSURE  OF  THE  AIR. 


39 


n 


eter,  but  the  others  require  longer  tubes  than 
the  mercurial  one  ;  besides,  most  liquids  evap- 
orate readily,  thus  changing 
the  height  of  the  liquid  col- 
umn, destroying  the  vacuum, 
and  altering  the  instrument. 
Mercury  at  ordinary  temper- 
atures evaporates  but  very 
little. 

Another  form  of  the  ba- 
rometer, and  a  favorite  one 
because  of  its  handiness, 
strength,  and  because  it  is 
easily  carried,  is  the  aneroid. 
An  aneroid  is  made  by  empty- 
ing of  air  a  drum-shaped 
steel  box  the  heads  of  which 
are  thin  enough  to  yield  a 
little  with  increase  of  air 

pressure.        The     motions    of   FIG.  8.— The  m^curial 

the  heads   can  be   made  to 
move  a  hand  which  marks 


barometer.  The  glass 
tube  held  on  the  right 
hand  is  closed  at  B. 
It  is  reversed  in  a 
the  amount  of  change.  These  basin  of  mercury  on 

the  left  hand  and  the 
mercury  in  the  tube 
falls  to  n, 


instruments  are  quite  sensi- 
tive,   and    large    ones   show     point  jt  js 
very  minute  variations  of  air     bv 
pressure,  but  they  change  too 
much  with  changes  of  tern- 


y  the  pressure  of  the 
air  on  the  surface 
of  the  mercury  in 
the  basin.  The  space 
above  n  is  a  vacuum. 


40  ABOUT  THE  WEATHER. 

perature  to  be  satisfactory  for  very  accurate 
observations.  The  box  is  under  a  high  strain 
at  all  times,  and  the  thinner  drumheads  gradu- 
ally change  under  this  strain,  until  the  instru- 
ment ceases  to  work  satisfactorily. 

The  pressure  of  the  air  is  usually  ex- 
pressed in  terms  of  the  height  of  the  column 
of  mercury  which  it  sustains.  In  English  this 
is  given  in  inches,  but  in  other  languages  it 
is  usually  given  in  millimetres.  On  maps 
and  diagrams  lines  called  isobars  are  drawn 
through  places  having  the  same  air  pressure. 


FIG.  9. — The  aneroid  barometer.  M  is  the  corrugated  vacuum 
box.  The  rest  consists  of  appliances  for  transmitting  its 
changes  to  the  arrow  or  pointer. 


CHAPTEE  VI. 

CHANGES    IN   THE   PEESSUEE    OF   THE   AIK. 

THE  pressure  of  the  air  is  neither  uniform 
nor  stationary,  but  it  is  different  in  different 
places  and  changes  in  all  sorts  of  ways.  The 
pressure  given  in  the  preceding  chapter  is,  on 
the  average,  that  for  the  northern  United 
States  at  or  near  sea  level. 

In  the  first  place  it  decreases  as  we  ascend. 
At  the  level  of  the  sea  the  whole  weight  of  the 
air  above  our  heads  is  pressing  upon  us,  but 
up  a  thousand  feet  higher  there  is  much  less 
air  above  us,  and  consequently  much  less 
pressure.  The  change  would  be  uniform  if 
the  air  were  not  elastic,  but  its  elasticity  is 
very  great.  It  yields  readily  to  pressure,  and 
the  result  is  that  the  lower  layers  are  con- 
densed, and  the  most  of  the  air  is  in  the  low- 
er layers,  where  man  makes  his  home.  Al- 
though the  atmosphere  is  four  hundred  and 
fifty  or  five  hundred  miles  deep,  fully  half 
the  air  is  in  the  first  three  and  a  half  miles, 

41 


42  ABOUT  THE  WEATHER. 

and  three  quarters  in  the  first  six  miles.  The 
difference  is  very  plain,  as  may  be  seen  in  the 
barometer,  at  Chicago.  Nearly  a  fifth  of  the 
air  is  below  the  top  of  Mt.  Washington.  At 
Santa  Fe,  New  Mexico,  or  in  the  City  of  Mex- 
ico, the  inhabitants  have  air  to  breathe  that  is 
less  than  four  fifths  as  dense  as  it  is  at  the  sea 
level.  At  Leadville  (the  highest  city  in  the 
United  States)  fully  one  third  of  the  air  is  be- 
low, and  on  the  top  of  Pike's  Peak  nearly  one 
half.  In  the  highest  ascent  which  man  has 
made  in  a  balloon  the  barometer  went  down 
to  seven  inches,  and  more  than  three  quarters 
of  the  air  was  below.  This  was  at  about  seven 
miles  above  the  sea. 

At  an  elevation  of  eight  thousand  two  hun- 
dred feet,  about  one  quarter  of  the  air  is  be- 
low, one  half  at  eighteen  thousand  feet,  and 
three  quarters  at  thirty-one  thousand  two  hun- 
dred feet.  Beginning  at  the  sea  level  the 
barometer  falls  at  the  rate  of  an  inch  for  each 
thousand  feet  of  elevation,  but  higher  up  the 
change  grows  slower.  In  drawing  isobars  on 
a  map  a  change  is  made  to  have  them  all  re- 
duced to  sea  level.  This  is  done  by  adding  to 
the  reading  for  any  station  about  one  inch  for 
every  thousand  feet  of  elevation. 

There  is  also  a  slight  difference  for  different 


CHANGES  IN  THE  PRESSURE  OF  THE  AIR.       43 

places  at  sea  level.  The  barometer  is  lowest 
along  the  equator,  and  highest  in  the  middle 
latitudes.  It  decreases  again  toward  the  poles, 
but  is  not  so  low  there  as  at  the  equator. 

The  pressure  on  the  whole  tends  to  be 
both  highest  and  lowest  over  the  great  oceans. 
There  is  an  area  of  high  pressure  on  the  Atlan- 
tic Ocean,  in  the  region  of  the  Sargasso  Sea,  be- 
tween the  Madeira  Islands  and  the  Bermudas. 
It  changes  its  place  back  and  forth  in  the  year, 
being  about  mid  ocean  and  farther  south  in  win- 
ter, and  near  the  Azores  in  summer.  There  is 
a  similar  one  in  the  South  Atlantic.  Over  the 
Pacific  Ocean  there  is  a  corresponding  pair  of 
areas,  but  they  hug  the  American  coast  more 
closely  than  do  the  permanent  centers  of  high 
pressure  over  the  Atlantic.  The  Indian  Ocean 
has  a  single  center  of  this  sort  about  midway 
between  Australia  and  the  Cape  of  Good  Hope. 
These  permanent  centers  of  high  pressure  seem 
to  play  an  important  part  in  guiding  the  paths 
of  traveling  storms.  Such  storms  generally 
travel  along  the  margin  of  these  areas  and  on 
the  side  toward  the  poles,  being  on  the  north 
side  in  the  northern  hemisphere,  and  on  the 
south  side  in  the  southern.  The  great  storms 
which  start  on  the  equatorial  side  of  these  cen- 
ters are  more  intense  and  destructive  than 

5 


44  ABOUT  THE  WEATHER. 

any  others.  Fortunately,  they  are  few  in 
number. 

The  pressure  also  changes  a  little  each  day 
of  the  year.  The  change  is  not  great ;  it  con- 
sists of  a  little  wave  of  pressure,  the  crest  of 
which  precedes  noon  and  midnight  by  about 
two  hours.  The  hollow  of  the  wave  passes  at 
about  four  o'clock  in  the  morning  and  after- 
noon. The  wave  is  a  small  one,  rarely  sur- 
passing an  eighth  of  an  inch  in  height,  and 
decreases  from  the  equator  to  the  pole.  It  is  so 
very  regular  that  in  the  tropics  it  will  almost 
serve  to  set  clocks  by.  It  is  probably  due  to 
the  great  changes  of  temperature  produced 
daily  by  the  sun.  It  is  less  in  the  cold  sea- 
sons and  in  cold  climates. 

There  is  also  a  change  of  pressure  with  the 
season.  The  air  pressure  is  greater  in  winter 
and  less  in  summer.  Over  great  continents  this 
difference  is  very  noticeable,  and,  especially 
when  the  climate  is  dry,  a  winter  center  of 
high  pressure  is  likely  to  form  over  the  conti- 
nent. This  is  not  very  noticeable  over  North 
America,  but  over  Asia  it  produces  a  great  cen- 
ter which  gives  the  highest  winter  pressures  on 
the  globe.  A  smaller  center  of  this  sort  is 
formed  over  the  desert  regions  of  South  Africa. 

On  the  other  hand,  there  are  three  centers 


CHANGES  IN  THE   PRESSURE  OF   THE  AIR.       45 

of  low  pressure  formed  on  the  northern  hemi- 
sphere which  continue  in  the  same  place,  or 
nearly  so,  during  the  season.  Those  of  most 
interest  to  us  are  over  the  North  Atlantic  and 
Pacific.  The  first  lies  between  Iceland  and 
Cape  Farewell,  and  it  is  toward  it  that  the 
storms  direct  their  course  after  leaving  the 
United  States.  The  storms  usually  pass  along 
the  southern  border  of  the  last-mentioned  cen- 
ter and  disappear  to  the  eastward  of  it.  The 
second  center  lies  along  the  Aleutian  Islands, 
and  is  not  so  intense  as  the  first.  It  is  from  its 
direction  that  a  great  many  of  our  storms 
come,  and  toward  it  go  the  Japanese  storms. 

These  centers  belong  to  the  cold  or  stormy 
season.  During  the  warm  season  one  such 
standing  center  of  low  pressure  forms  over 
southern  Asia.  It  controls  the  summer  mon- 
soons so  important  to  that  continent. 

The  pressure  also  changes  with  the  weather, 
and  its  changes  are  the  best  guides  to  the  latter. 
When  air  rises  it  presses  downward  with  less 
weight,  and  the  barometer  is  then  lower.  In 
the  same  way  when  air  descends  the  pressure 
due  to  its  motion  is  added  to  the  ordinary 
pressure,  and  the  barometer  is  higher.  The  air 
rises  in  the  general  storms,  and  in  some,  if  not 
all,  of  the  local  ones,  and  it  falls  in  clear  and 


46  ABOUT  THE  WEATHER. 

calm  weather.  So  a  lower  barometer  is  found 
in  stormy  weather  and  a  high  barometer  when 
it  is  clear  and  calm. 

The  cooling  of  the  air  by  expansion  is  very 
important,  because  the  making  of  clouds  chiefly 
depends  upon  it.  Air  rises,  and  as  it  gets  into 
the  higher  regions  it  is  in  some  measure  relieved 
of  pressure.  It  then  expands  and  cools,  and 
its  moisture  is  in  part  condensed,  making 
clouds. 

We  bear  without  discomfort  the  enormous 
pressure  of  the  air ;  so  completely  balanced  is 
it  that  we  feel  it  no  more  than  does  the  scale 
pan  of  a  balance  feel  the  pressure  on  its  upper 
and  lower  sides.  The  healthy  human  body  is 
not  sensitive  to  changes  of  pressure  unless  they 
are  very  great.  Variations  of  the  weather  fre- 
quently introduce,  rather  slowly  to  be  sure, 
changes  of  from  a  thirtieth  to  a  fifteenth  of  the 
entire  air  pressure — but  our  sensations  tell  us 
nothing  of  it.  We  can  travel  from  the  sea- 
board to  Leadville  in  three  days  and  rid  our- 
selves of  two  fifths  of  the  air  pressure  and  yet 
not  be  conscious  of  it  unless  we  engage  in 
severe  exertion,  such  as  running  or  climbing. 
If  we  ride  to  the  top  of  Pike's  Peak  or  Mont 
Blanc  there  will  be  little  discomfort,  though 
the  air  is  scarcely  more  than  half  as  dense  as 


CHANGES  IN  THE  PRESSURE  OP  THE  AIR.       47 

at  sea  level.  The  so-called  mountain  sickness 
is  due  rather  to  severe  and  unusual  exertion 
than  to  changes  in  air  pressure  alone.  It  re- 
mains to  be  said,  however,  that  any  great  or 
sudden  change  is  dangerous  to  persons  whose 
lungs  are  not  sound,  because  the  blood  vessels 
of  the  lungs  are  rendered  tender  by  disease  and 
may  burst. 

The  lighter  air  of  mountain  tops  causes  the 
healthy  to  breathe  more  deeply.  The  lungs 
can  expand  very  much  more  than  they  do  at 
lower  levels.  There  is  a  limit  to  this  expan- 
sion, however,  and  when  we  pass  this,  suffering 
ensues  It  comes  on  at  different  elevations  for 
different  people,  but  in  general  at  an  elevation 
more  than  twenty  thousand  feet  the  air  would 
be  so  thin  as  to  bring  on  distress.  Glaisher, 
who  ascended  in  a  balloon  to  thirty -seven  thou- 
sand feet,  when  the  barometer  registered  only 
seven  inches,  was  greatly  distressed  and  fainted 
away. 


CHAPTER  VII. 

THE    WINDS  :    THEIR    KINDS    AND    DISTRIBUTION. 

WIND  is  due  to  the  tendency  of  the  air  to 
equalize  its  pressure.  When  the  pressure  at 
any  place  is  less  than  that  around  it,  the  air 
flows  in  to  make  the  pressure  uniform.  As 
the  air  is  always  flowing  here  and  there  in  its 
disposition  to  equalize  the  pressure  and  bring 
the  atmosphere  to  a  uniform  and  quiet  state, 
one  might  expect  that  it  would  at  last  succeed 
and  everything  become  calm.  And  entire  free- 
dom from  disturbance  would  without  doubt 
come  to  pass  were  it  not  for  the  heat  which  the 
sun  pours  out  on  the  earth.  This  is  not  dis- 
tributed uniformly  as  to  time  or  place,  for  it 
comes  in  the  daytime  only,  and  is  less  in  the 
higher  latitudes,  or  in  proportion  to  the  length 
of  the  shadow  the  sun  casts  at  noon.  The 
regularities  of  the  heat  are  constantly  interfer- 
ing with  the  endeavors  of  the  wind  to  smooth 
out  the  irregularities  of  the  atmospheric  pres- 
sure, and  the  work  never  ends. 

48 


WINDS:   THEIR  KINDS  AND   DISTRIBUTION.       49 

The  sun's  rays  warm  up  the  air  next  to  the 

earth  more  in  some  spots  than  others,  for  the 

amount  of  heat  received  at  any  particular  spot 

depends  largely  on  the  color  of  the  soil,  the 

amount  of  moisture  it  holds,  its  protection  from 

the  wind,  the  shade,  the  clouds,  and  other  things. 

/The  warmer  air  becomes  lighter,  expands,  and 

/  sooner  or  later  rises.     The  cooler  air  around 

1  flows  in  to  take  its  place,  and  so  a  wind  comes 

\into  existence.    It  may  be  brief  and  gentle  when 

the  disturbance  is  slight  and  local,  or  it  may  be 

great  and  continue  long,  if  the  disturbance  has 

these  characteristics.    And  when  it  once  arises, 

it  may  have  features  which  will  perpetuate  it, 

as  we  shall  see  later. 

A  brief  and  gentle  disturbance  of  this  sort, 
familiar  to  every  one,  is  the  little  dust-whirl, 
seen  at  its  best  over  a  dusty  road  on  a  hot, 
calm  summer  afternoon.  The  air  in  contact 
with  the  dust  becomes  hotter  and  hotter  until 
at  some  point,  determined  perhaps  by  a  small 
projecting  stone  or  the  flight  of  a  bird  or  in- 
sect, it  breaks  through  the  cooler  stratum  of 
air  above,  and  for  a  few  seconds  forces  itself 
up ;  then  comes  a  quick  inflow  of  air  along  the 
ground,  bringing  dust  with  it  for  a  short  dis- 
tance around.  This  inflow  whirls  because  it 
comes  in  unequally  from  the  sides.  The  cause 


50 


ABOUT  THE  WEATHER. 


of  the  whirl  is  local  and  temporary,  and  the  little 
reservoir  of  hot  air  is  soon  exhausted,  the  dust 
whirls  in  a  beehive  or  spindle  form  for  a  few 
seconds,  sweeps  off  in  a  jerky  way  to  one 
side  or  the  other,  and  comes,  aimlessly  to  the 
ground,  bringing  to  a  close  a  very  brief  but 


FIG.  10. — A  summer  dust-whirl  over  a  country  road.    The  direc- 
tion of  motion  is  against  the  hands  of  a  watch. 

pretty,   interesting,    and    instructive    phenom- 
enon. 

On  a  great  scale  the  same  general  phenom- 
enon occurs  on  the  ocean  in  the  calm  latitudes 
not  far  from  the  equator,  and  there  produces 
those  large  and  very  destructive  storms  called 
typhoons  and  hurricanes,  causing  terrific  inflow- 
ing winds,  traveling  forward  in  well-defined 
paths,  and  lasting  several  days.  Every  grada- 
tion between  the  little  dust-whirl  and  the  enor- 
mous hurricane  can  be  found,  and  the  laws  in- 


WINDS:   THEIR  KINDS  AND  DISTRIBUTION.       51 

volved  in  the  two  are  the  same,  except  that  in 
the  greater  and  more  lasting  cyclones  moisture 
or  steam  plays  a  part. 

When  the  air  next  the  soil  or  the  ocean  sur- 
face becomes  hot  it  passes  into  a  condition  of 
unstable  equilibrium,  like  dynamite  or  gun- 
powder. It  then  requires  but  very  little  to 
destroy  the  uncertain  balance  and  cause  the  hot 
air  to  rise  with  a  rush.  A  hurricane  may  be 
started,  when  everything  is  just  ready,  by  the 
slightest  thing — the  motion  of  a  bird  through 
the  air,  for  instance. 

A  current  started  downward  by  cold  or  by 
the  air  that  rises  elsewhere,  may  cause  a  higher 
pressure,  and  the  air  must  flow  away  from  it. 
For  instance,  the  air  on  a  hilltop  or  mountain 
gets  chilled  on  a  clear  night.  This  increases 
its  density — makes  it  heavier — and  it  will  flow 
down  into  the  valleys,  displacing  the  air  there. 
Air  from  behind  follows  it,  and  thus  a  system 
of  winds  is  set  up. 

The  differences  of  temperature  make  ascend- 
ing and  descending  currents,  and  these  cause 
horizontal  motions  of  the  air.  The  ascending 
and  descending  currents  are  not  directly  felt 
by  us,  because  we  are  at  the  bottom  of  the 
ocean  of  air  in  which  they  occur.  When  in  the 
free  air — that  is,  anywhere  else  than  on  hill 


52 


ABOUT  THE  WEATHER. 


WINDS:   THEIR   KINDS  AND  DISTRIBUTION.       53 

or  mountain  slopes — they  can  be  felt  only  at 
some  distance  above  the  surface.  Our  knowl- 
edge of  them  is  obtained  chiefly  through  rea- 
soning; but  the  study  of  the  clouds  helps  us 
much.  The  important  part  played  in  the 
weather  by  ascending  and  descending  currents 
of  air  will  become  plainer  as  we  proceed. 

The  horizontal  winds  near  the  earth's  sur- 
face are  those  that  we  feel,  and  such  we  know 
very  well.  These  comprise  the  general  ter- 
restrial system,  the  storm  system,  the  annual 
and  diurnal  winds,  and  certain  occasional  winds 
due  to  mountains  and  hills. 

Almost  under  the  path  of  the  sun  each 
day  lies  the  heat  equator.  It  moves  back  and 
forth  each  side  of  the  equator  proper  as  the 
sun  comes  north  in  summer  or  goes  south  in 
winter.  Along  the  heat  equator  the  sun's  rays 
warm  the  air  and  cause  it  to  £ise,  so  that  there 
is  a  ring  of  rising  air  around  the  earth  all  the 
time.  Under  this  ring  the  air  is  nearly  calm, 
and  above  it  there  is  more  or  less  cloudiness. 

To  supply  the  place  of  the  air  which  }ises, 
the  wind  flows  into  the  region  of  the  heat 
equator.  On  the  north  side  it  flows  south- 
ward, and  on  the  south  side  northward.  The 
rotation  of  the  earth  makes  this  wind  fall  back 
in  its  progress  toward  the  equator,  so  that  on 


54  ABOUT  THE  WEATHER. 

the  north  side  there  is  a  ring  of  inflowing 
winds  from  the  northeast  known  as  the  north- 
east trade  winds.  They  are  called  trade  winds 
because  they  help  commerce,  being  fairly  con- 
stant and  steady  over  the  ocean.  On  the  south 
side  of  the  equator  there  is  a  corresponding 
ring  of  southeast  trades. 

These  rings  extend  about  twenty  degrees 
from   the  heat  equator  on  each  side   on   the 


s 

FIG.  12. — Rings  and  caps  of  the  earth  as  shown  in  the  winds. 

oceans.  On  the  land  they  are  much  broken 
up  by  mountain  ranges  and  other  features, 
which  cause  local  weather  conditions.  Beyond 
these  rings  on  each  hemisphere  comes  a  broad 
ring  or  zone  of  variable  weather,  where  the 


WINDS:   THEIR  KINDS  AND  DISTRIBUTION.       55 

winds  are  controlled  by  storms.  And  beyond 
these  come  the  polar  caps,  the  weather  of  which 
is  not  well  known. 

Thus  we  have  for  each  hemisphere,  count- 
ing from  the  heat  equator,  three  rings  and  a 
cap  of  weather — the  calm  and  quiet  weather 
about  the  heat  equator,  the  settled  weather  of 
the  trade  latitudes,  the  variable  weather  of  the 
temperate  zones,  and  the  less  known  but  prob- 
ably strong  and  variable  weather  of  the  polar 
caps. 

It  is  in  the  zones  of  variable  weather,  ap- 
parently, that  the  air  which  ascends  at  the 
equator  begins  to  come  down  to  the  earth's 
surface  again.  The  result  is  the  prevailing 
winds  from  the  west  which  occur  in  these  zones 
when  the  weather  is  not  controlled  by  storms. 


CHAPTEK  VIII. 

DIRECTION,  VELOCITY,  AND    MEASUREMENT  OF  THE 
WINDS. 

THE  winds  are  named  from  the  direction  in 
which  they  come  to  us.  A  wind  that  comes 
from  the  northeast  and  travels  to  the  south- 
west is  called  a  northeast  wind.  The  direction 
is  indicated  by  the  wind  vane,  and  this  always 
points  to  the  direction  from  which  the  wind 
comes. 

The  velocity  of  the  wind  is  expressed  in 
the  miles  it  travels  per  hour.  A  very  light 
breeze,  just  enough  to  stir  the  leaves  on  the 
trees,  has  a  velocity  of  about  two  miles  per 
hour.  A  gentle  breeze,  which  cools  us  in 
summer,  travels  at  the  rate  of  from  five  to 
seven  miles  an  hour.  A  fresh  breeze  is  travel- 
ing at  the  rate  of  ten  or  twelve  miles ;  a  strong 
one  from  fifteen  to  twenty — or  at  the  rate  of  a 
freight  train ;  a  high  wind  from  twenty -five  to 
thirty,  and  a  gale  from  thirty-five  to  sixty — as 
fast  as  the  swiftest  express  train.  A  hurricane 

56 


VELOCITY  OP  THE  WINDS.  57 

may  have  winds  traveling  from  seventy-five 
to  nearly  one  hundred  miles  per  hour,  and  in 
tornadoes  the  velocity  may  be  still  higher. 

The  velocity  of  the  wind  may  be  measured 
by  any  sort  of  a  windmill,  but  the  form  which 
is  usually  adopted  is  that  of  four  hollow  hemi- 
spheres on  the  end  of  four  arms  turning  hori- 
zontally. A  measurer  of  the  wind  is  called  an 
anemometer,  and  this 
form  is  Robinson's  cup 
anemometer,  named 
from  the  man  who 
first  developed  its  use 
in  this  way.  The 
force  of  the  wind  is 
measured  in  several 
ways.  A.  simple  de- 
vice is  a  pendulum  _  ,  r^*", 

FIG.  13. — Robinson's  cup  anemom- 

which  the  moving  air       eter.     The  cups  move  with  the 

hands  of  a  watch. 

swings  out  to  a  greater 

or  lesser  extent-  from  a  vertical  position  and  so 
measures  the  force  of  the  wind.  Or  a  flat 
board  a  foot  square,  with  a  spring  behind  it, 
may  be  carried  on  a  wind  vane  so  as  to  be 
always  opposed  to  the  wind.  The  wind  will 
press  the  board  back  and  compress  a  spring. 
The  number  of  turns  made  is  counted  by  a 
little  device  much  like  that  on  a  gas  meter. 


58  ABOUT  THE  WEATHER. 

The  force  which  the  wind  exerts  differs 
with  the  form,  size,  and  position  of  the  surface 
exposed  to  it.  The  usual  rule,  which  gives 
a  fair  average  value,  is  that  the  pressure  in 
pounds  to  the  square  foot  may  be  obtained  by 
squaring  the  velocity  in  miles  per  hour  and 
dividing  by  two  hundred.  This  would  give  at 
fourteen  miles  per  hour  a  pushing  force  of  one 
pound  to  each  square  foot  directly  opposed  to 
it.  A  north  wind  of  fourteen  miles  would  make 
a  pressure  of  one  pound  on  each  square  foot 
against  walls  facing  the  north,  against  which  it 
blows.  This  is  not  a  severe  wind,  but  for  a 
small  house  it  would  give  a  pressure  of  four  or 
five  hundred  pounds  on  the  north  side.  For 
twenty  miles  an  hour  the  pressure  would  be 
two  pounds  to  each  square  foot ;  for  forty 
miles  (and  such  winds  are  not  rare),  eight 
pounds;  for  sixty  miles,  eighteen  pounds,  and 
so  on.  Buildings  must  be  made  strong,  for  a 
pressure  of  eight  pounds  to  the  square  foot 
means  one  or  two  tons,  and  of  eighteen  pounds 
to  the  square  foot  from  three  to  five  tons  push- 
ing force  against  a  small  house. 
.  It  is  this  power  that  is  used  in  windmills, 
but  they  are,  generally  speaking,  so  rude  as 
machines  that  much  of  it  is  lost.  The  larger 
the  mill,  the  less  effect  its  various  imperfec- 


MEASUREMENT  OF  THE   WINDS.  59 

tions  has,  so  that  while  a  mill  eight  feet  in 
diameter  uses  only  about  a  tenth  of  the  energy 
of  the  wind,  one  of  twenty-five  feet  uses  about 
a  third.  The  first  can  do  only  about  a  twenty- 
fifth  part  as  much  work  as  a  horse,  while  the 
last  does  about  a  third  more  than  an  average 
horse. 

The  wind  is  reduced  by  the  friction  of  the 
earth's  surface ;  its  velocity  is  less  on  land 
than  on  sea,  and  in  wooded  countries  than  over 
open  plains ;  it  is  less  when  it  is  close  to  the 
surface  than  when  it  is  higher  up,  and  it  attains 
its  greatest  average  velocity  at  a  distance  of 
some  thousands  of  feet  above  sea  level.  The 
wind  is  also  likely  to  change  during  the  day, 
and  averages  greater  in  the  afternoon  than 
during  the  rest  of  the  day.  It  often  goes  down 
perceptibly  when  the  sun  sets. 


CHAPTEK  IX. 

THE    TEMPERATURE    OF    THE    AIR. 

IN  records  of  the  weather  and  climate  the 
temperature  of  the  air  is  always  understood  to 
have  been  taken  in  the  shade.  In  the  sun  the 
temperature  is  higher  and  varies  to  some  extent 
with  the  material  and  color  of  the  thermometer 
used. 

The  highest  temperatures  on  the  earth  are 
generally  at  the  bottom  of  the  atmosphere.  As 
one  passes  up  the  temperature  falls,  and  it 
reaches  its  lowest  point  at  the  limit  of  the 
atmosphere.  How  low  it  is  there  is  not  known, 
but  it  is  several  hundred  degrees  Fahrenheit 
below  zero.  The  rate  of  fall  in  temperature 
varies  much  close  to  the  earth,  according  to  the 
season  and  the  weather.  At  first  it  averages 
about  three  degrees  for  every  thousand  feet, 
but  above  this  it  changes  more  slowly. 

At  the  earth's  surface  the  variations  of  the 
temperature  are  due  to  the  sun's  rays,  and  these 
are  so  hot  that,  after  losing  a  half  or  three 

60 


THE   TEMPERATURE   OF   THE  AIR.  61 

quarters  of  their  potency  in  passing  through 
the  atmosphere,  they  are  still  warm  enough, 
when  properly  applied,  to  cook  a  dinner  in  a 
Dutch  oven,  or  to  run  a  solar  machine. 

Much  of  the  heat  of  the  sun's  rays  is  lost  at 
the  upper  surface  of  the  clouds.  Much  which 
passes  through  the  clouds  or  comes  down 
through  the  clear  atmosphere  is,  in  fact,  ab- 
sorbed by  the  air  itself,  and  warms  it.  Another 
part  is  expended  in  warming  the  soil  and  water, 
and  still  another  in  evaporating  water,  chang- 
ing it  into  vapor  or  moisture.  All  this  heat, 
however,  is  returned  later  to  the  air,  and  the 
latter  is  better  able  to  absorb  it  when  thus  re- 
turned than  when  it  comes  directly  from  the 
sun.  The  heat  of  the  sun's  rays,  which  comes 
to  us  directly  only  in  the  day,  may  be  dis- 
tributed everywhere,  and  be  returned  to  the 
air  during  the  night. 

Heat  given  off  by  the  soil  or  wrater  is  more 
easily  absorbed — one  might  say  caught  or 
trapped — by  the  air  than  that  which  comes  di- 
rectly from  the  sun.  The  difference  between 
the  sun's  rays  and  the  heat  radiated  from  the 
soil  is  well  shown  in  the  hotbed  of  the  gar- 
dener. The  sun's  rays  pass  through  the  glass 
with  little  loss,  but  the  rays  reflected  from  the 
soil  can  not  pass  back  again  through  it  without 


62  ABOUT  THE  WEATHER. 

great  loss.  The  heat  is  thus  trapped  by  the 
glass,  and  the  temperature  inside  rises  much 
higher  than  that  outside. 

The  meteorological  temperatures  show  the 
balance  between  the  gains  and  losses  of  heat  by 
the  air.  The  losses  come  in  large  part  from  the 
reflection  and  radiation  of  the  heat  into  free 
space.  This  space  is  very  cold  and  takes  up  all 
the  heat  sent  to  it.  It  is  this  loss  that  causes 
unseasonable  frosts  on  clear  nights.  Another 
source  of  loss  is  found  in  the  heat  that  is  re- 
quired to  evaporate  water,  and  this  is  going  on 
all  the  time  and  at  all  temperatures.  Still  an- 
other loss  is  the  heat  used  in  warming  up  the 
soil  and  water  to  a  greater  or  less  depth. 

The  gains  are  as  numerous.  The  air  ab- 
sorbs a  part  of  the  heat  that  passes  through 
it.  The  heat  taken  up  in  evaporation  is 
given  out  again  when  the  vapor  is  condensed, 
and  this  may  be  at  a  great  distance  from  the 
place  where  it  was  absorbed ;  the  soil  gradually 
gives  out  its  heat  to  the  air,  and  so  does  the 
warmer  water;  thus  the  heat  comes  back  to 
the  air  again  ;  but,  as  a  result  of  these  processes 
and  of  the  delays  due  to  them,  as  well  as  of  the 
alternation  of  day  and  night,  the  supply  of  heat 
is  uneven  and  irregular  and  the  temperatures 
are  never  steady. 


THE  TEMPERATURE  OF  THE  AIR.  63 

The  temperature  is  lowest  at  night  and 
highest  in  the  daytime.  It  reaches  its  lowest 
point  on  clear  nights  at  about  daybreak,  and  its 
highest  at  about  three  in  the  afternoon.  It  is 
also  lowest  in  winter  when  the  sun  passes  near- 
est the  horizon,  and  it  is  highest  in  summer 
when  the  sun  comes  up  nearest  to  the  zenith. 
The  coldest  days  are  in  the  latter  half  of  Janu- 
ary, and  the  warmest  in  the  latter  half  of  July. 

The  temperature  is  also  very  much  modified 
by  clouds.  A  layer  of  clouds  is  a  sunshade  by 
day  and  a  blanket  by  night.  It  keeps  the  day 
cooler  and  the  night  warmer.  Hence  in  stormy 
weather  the  temperature  is  more  even,  in  clear 
weather  more  variable.  The  barometer  and 
thermometer  usually  move  in  opposite  direc- 
tions. When  one  falls  the  other  rises. 

The  highest  temperatures  ever  observed  in 
the  shade  have  been  in  deserts  not  far  from 
the  equator ;  they  run  up  to  about  140°  F. ; 
the  very  highest  recorded  is  154°  F.  from  the 
Sahara.  The  lowest  known  are  from  the  great 
land  areas  under  the  arctic  circle,  in  Siberia 
and  North  America.  They  run  down  to  —  50°  or 
—  60°  below  zero ;  and  the  very  lowest  recorded 
was  —  96°  below  zero,  in  northeastern  North 
America.  Thus  the  absolute  range  of  tempera- 
tures observed  on  the  earth  is  250°.  In  the 


64  ABOUT  THE  WEATHER. 

United  States,  outside  Alaska,  the  range  is 
probably  not  two  thirds  of  that,  and  for  any 
particular  well-populated  place  about  half. 

The  temperatures  are  measured  by  a  ther- 
mometer hung  in  the  shade,  and  free  from  all 
bodies  which  can  conduct  heat  to  it.  The  usual 
form  is  the  mercurial  thermometer ;  but  the 
mercury  used  in  it  freezes  at  very  low  tem- 
peratures, and  in  high  latitudes  it  must  be  re- 
placed by  a  spirit  thermometer.  There  are 
unfortunately  two  different  thermometer  scales 
in  ordinary  use.  The  first  is  that  used  by  Eng- 
lish-speaking people  generally,  and  is  called  the 
Fahrenheit  scale,  from  the  name  of  the  man 
who  invented  it.  On  this  the  freezing  point 
for  water  is  32°,  and  the  boiling  point  212°. 
The  other  is  that  called  the  Celsius  scale,  from 
its  inventor,  but  more  often  the  Centigrade, 
from  the  number  of  degrees  between  freezing 
and  boiling.  The  zero  of  this  scale  is  at  the 
freezing  point  of  water,  and  100°  at  the  boiling 
point.  Thus  the  Fahrenheit  scale  has  180°  be- 
tween freezing  and  boiling,  and  the  Centigrade 
100°.  The  Centigrade  scale  is  usually  employed 
by  people  other  than  those  speaking  English, 
and  by  the  latter  in  scientific  work.  In  this 
book  all  the  temperatures  given  are  those  on 
the  popular  or  Fahrenheit  scale. 


THE  TEMPERATURE   OP  THE  AIR.  65 

Lines  passing  through  places  on  the  map 
having  the  same  temperatures  are  called  iso- 
therms. They  correspond  to  the  isobars  for 
pressure.  The  isotherms  on  the  weather  map 
are  usually  drawn  for  each  ten  degrees. 


CHAPTEK  X. 

HUMIDITY,    OE   MOISTURE. 

BY  humidity  is  meant  the  invisible  water 
in  the  form  of  vapor  or  gas  in  the  air.  Steam 
is  another  name  for  the  vapor  of  water,  and  is 
the  same,  whether  it  arises  out  of  water  by  the 
slow  process  of  evaporation  from  the  surface, 
or  that  more  rapid  process  of  evaporation, 
throughout  the  mass  which  we  call  boiling. 
What  comes  from  the  teakettle  or  from  steam- 
cocks  is  condensed  steam — of  the  same  char- 
acter as  fog  and  cloud.  Humidity,  moisture, 
the  vapor  of  water  or  steam,  is  invisible,  but 
when  it  condenses  in  the  air  it  forms  drop- 
lets, which  when  small  are  white.  In  this 
sense  steam  exists  at  all  temperatures.  It  is 
only  the  surplus  steam  or  moisture  that  con- 
denses. 

Matter  has  three  physical  states,  the  solid, 
the  liquid,  and  the  gaseous,  and  the  change 
from  one  to  the  other  is  made  by  the  addition  or 
subtraction  of  heat.  To  change  a  body  from 

66 


HUMIDITY,  OR  MOISTURE.  67 

solid  to  liquid,  as  when  ice  or  iron  is  melted, 
or  from  liquid  to  gas  as  when  alcohol  or  water 
is  evaporated — heat  must  be  added.  When 
the  change  is  the  other  way,  heat  is  given  out. 
It  always  takes  the  same  amount  of  heat  to 
make  any  and  all  these  changes  in  the  same 
substance. 

The  ordinary  natural  substances  remain  un- 
changed through  the  whole  range  of  weather 
temperatures  ;  iron  remains  solid,  and  the  met- 
als, rocks,  and  soil  are  unmelted  through  all 
weather  changes.  On  the  other  hand,  all  the 
gases  of  the  atmosphere  remain  gaseous  through- 
out the  weather  changes.  Oxygen,  nitrogen, 
and  carbonic-acid  gas  require  enormously  lower 
temperatures  than  the  weather  makes  to  change 
them  to  liquids. 

The  only  natural  and  common  substance 
that  changes  its  physical  state  in  the  range 
of  meteorological  changes  is  water,  and  it  passes 
through  the  series  of  three  steps.  In  winter  it 
is  often  solid  and  when  high  up  in  the  air  it  may 
be  in  solid  particles  in  summer.  Its  solid  forms 
are  ice,  snow,  hail,  hoarfrost,  and  minute  ice 
spicules.  In  high  latitudes  in  winter  liquid 
water  can  be  obtained  only  by  melting  ice.  In 
summer  and  in  the  tropics  water  in  the  solid 
form  does  not  exist  at  the  surface,  but  may  do 


68  ABOUT  THE   WEATHER. 

so  on  mountain  tops  or  at  some  considerable 
elevation  in  the  air. 

The  change  from  ice  to  water  occurs  at 
the  temperature  of  32°  F.,  but  that  from  ice  or 
water  to  moisture  or  vapor  may  occur  at  any 
temperature.  There  is  always  a  considerable 
amount  of  water  vapor  in  the  air,  but  much 
more  in  the  summer  than  in  the  winter. 

This  change  in  the  physical  state  of  water 
is  going  on  constantly,  and  with  each  change 
heat  is  absorbed  or  given  out  with  a  corre- 
sponding change  in  the  temperature  of  the  air. 
If  the  water  is  condensed  it  warms  the  air? 
and  if  it  is  evaporated  the  air  is  cooled,  and 
this  heat,  taken  up  at  one  place  may  be  given 
out  at  a  far  distant  one.  We  can  think  of 
the  molecule  of  water  as  a  porter  carrying  its 
little  load  of  heat  from  the  place  where  it  was 
evaporated  to  the  place  where  it  is  to  be  con- 
densed. This  may  be  a  distance  of  hundreds, 
perhaps  thousands  of  miles,  and  the  heat  taken 
up  at  the  surface  may  be  liberated  high  up  in 
the  free  air. 

Water  is  the  carrier  and  distributor  of  heat 
in  the  atmosphere.  It  gives  drink  to  all  thirsty 
things  in  Nature,  whether  they  are  organic  or 
inorganic.  In  the  air  also  it  is  the  only  impor- 
tant gaseous  element  that  varies,  and  to  it  are 


HUMIDITY,   OR  MOISTURE.  69 

due  many  varying  properties  of  the  atmosphere. 
For  instance,  it  is  lighter  than  air,  and  by  its 
less  weight  and  variable  amount  it  changes  the 
density  and  the  weight  per  cubic  foot  of  the 
air.  If  we  add  to  the  offices  of  water  these 
others — that  there  are  many  chemical  combina- 
tions which  could  not  take  place  without  water, 
that  water  is  the  only  great  natural  liquid  of 
Nature,  and  that  it  aids  in  transferring  many 
substances  by  holding  them  in  solution — we 
will  understand  how  important  this  familiar 
substance  is.  And  in  no  domain  of  Nature  is 
it  more  important  than  in  the  work  of  the 
atmosphere. 

In  its  gaseous  or  vapor  state  of  humidity 
it  comes  from  evaporation,  and  this  process 
constantly  goes  on  from  all  surfaces  containing 
water,  unless  the  air  in  contact  with  such  sur- 
faces is  saturated ;  it  goes  on  even  from  ice  as  is 
shown  by  the  way  ice  slowly  dwindles  with- 
out melting  if  the  air  is  very  dry. 

But  evaporation  occurs  not  only  from  the 
surface  of  water,  but  from  all  surfaces  which 
are  moist.  This  is  the  constant  drying-out 
process,  and  the  vapor  poured  from  the  sur- 
face of  moist  soil  may  be  more  abundant  than 
from  that  of  pure  water,  as  from  a  surface 
covered  with  living  turf,  for  the  grass  is  chiefly 


ft)  ABOUT  THE   WEATHER. 

occupied  in  pumping  water  from  below,  and 
throwing  it  out  into  the  air  as  vapor.  It  does 
this  in  order  to  get  the  nourishment  it  needs, 
which  is  held  in  solution  in  the  water. 

Moisture,  then,  is  constantly  passing  into 
the  air  by  evaporation.  By  this  process  the 
molecule  of  water  casts  off  the  bonds  that  held 
it  to  other  molecules  and  is  free  to  travel  for 
itself  through  space.  It  does  this,  and  its  mo- 
tion is  so  rapid  that  it  is  soon  far  away  from 
the  spot  where  it  gained  its  freedom.  The 
diffusion  of  the  vapor  of  water  through  the  air 
is  far  more  rapid  than  its  distribution  by  the 
winds  could  be. 

The  limits  to  this  diffusion  are  to  be  found 
in  temperature.  The  lower  the  temperature, 
the  fewer  the  molecules  which  have  freedom 
of  motion.  If  there  are  too  many,  the  sur- 
plus molecules  must  combine  in  the  process 
of  condensation  to  make  dew  or  hoarfrost,  fog 
or  cloud,  or  hailstone,  or  some  other  form  of 
water  or  ice.  If  the  temperature  rises,  a  part 
or  all.  of  these  may  pass  back  into  the  vapor 
state ;  if  it  falls,  more  vapor  is  condensed. 
The  temperature  at  which  condensation  begins 
is  called  the  dew-point.  At  the  dew-point  the 
air  is  saturated — that  is,  at  the  temperature 
called  by  this  name  the  air  has  as  much  mois- 


HUMIDITY,    OR  MOISTURE.  71 

tare  as  it  can  accommodate.  If  the  tempera- 
ture rises,  more  water  can  be  evaporated — and 
will  be,  if  it  is  available ;  if  the  temperature 
falls  below  the  dew-point,  some  of  the  moisture 
will  be  condensed. 

The  amount  of  moisture  in  the  air  is  ex- 
pressed by  its  weight  in  grains  to  each  cubic 
foot.  This  amount  is  called  the  absolute  hu- 
midity. The  absolute  humidity  for  saturation 
at  30°  below  zero  is  only  an  eighth  of  a  grain. 
At  0°  it  is  over  half  a  grain,  at  32°  about 
two  grains,  at  60°  nearly  six  grains,  and  at  100° 
it  is  twenty  grains.  The  absolute  humidity  is 
less  in  winter  than  in  summer,  at  night  than 
in  the  day,  in  cold  climates  than  in  hot,  and 
it  decreases  rapidly  as  one  ascends  in  the  air. 

The  vapor  of  water  in  the  air  may  be  looked 
on  as  an  atmosphere  in  itself.  As  such  it  is 
much  lighter  than  the  dry  air,  and  its  depth  is 
perhaps  much  less  than  that  of  the  dry  atmos- 
phere, for  the^  humidity  thins  out  rapidly  up- 
ward. As  an  atmosphere,  however,  it  exerts 
a  pressure  of  its  own,  which  is  often  used  by 
meteorologists,  and  is  called  the  vapor  tension. 
It  is  very  much  less  than  the  pressure  of  the 
dry  air,  being  generally  less  than  an  inch  of 
mercury,  and  very  rarely,  under  the  most  favor- 
able circumstances,  being  more  than  two  inches. 


72  ABOUT  THE  WEATHER. 

In  practical  questions,  involving  the  drying- 
out  quality  and  the  rapidity  of  evaporation  of 
the  air,  another  expression  is  used  for  the  hu- 
midity. This  is  relative  humidity,  an  ex- 
pression of  the  ratio  between  the  moisture 
the  air  contains  and  that  which  it  would  con- 
tain if  it  were  saturated.  For  instance,  if  the 
air  has  only  half  as  much  moisture  as  it  could 
hold,  the  relative  humidity  is  0.50  ;  if  three 
quarters,  0.75.  Usually  the  decimal  point  is 
left  off,  and  these  numbers  are  simple  percent- 
ages. Commonly  the  relative  humidity  is 
above  75.  If  it  is  between  that  and  50,  things 
dry  out  and  furniture  becomes  loose  in  the 
joints.  Below  50  the  drying  is  rapid  and  the 
sensation  of  dryness  is  distinct.  In  some  des- 
ert places  the  relative  humidity  may  descend 
to  10,  or  even  5,  and  lower. 

The  accurate  measurement  of  the  humidity 
of  the  air  requires  an  elaborate  experiment. 
Meteorologists  have  contented  themselves  with 
a  less  direct  method,  where  two  thermometers 
are  used,  one  with  its  bulb  wetted,  the  other 
with  its  bulb  dry.  The  cooling  due  to  evap- 
oration is  thus  obtained,  and  from  this  and 
the  temperature  the  humidity  may  be  calcu- 
lated. 


CHAPTER  XL 

DEW,  FOG,  AND    CLOUD. 

WHEN  condensation  occurs  the  free  and  in- 
dependent molecules  of  the  vapor  must  rush  to- 
gether to  enter  again  into  the  closer  bonds  of  a 
liquid.  There  are  probably  myriads  of  them 
in  each  droplet  of  dew,  fog,  or  cloud  that  is 
formed.  That  they  rush  together  is  due  to  the 
fact  that  there  is  not  enough  heat  present  to 
keep  them  apart.  The  point  toward  which 
they  rush  is  determined  by  such  solids  or 
liquids  as  happen  to  be  already  present. 

In  the  case  of  the  dew  free  surfaces  on 
which  the  condensing  water  is  deposited  are 
furnished  by  the  soil,  stones,  plants,  and  other 
things  in  connection  with  the  ground.  When 
the  sky  is  clear  and  they  are  not  heated  by  the 
sun,  these  objects  lose  heat  by  radiation  and 
become  chilled.  If  at  the  same  time  the  air  is 
still  it  becomes  chilled  by  contact  with  the  rock 
or  other  body,  and  deposits  upon  it  the  con- 
densed  moisture.  The  operation  can  be  seen 

73 


74  ABOUT  THE  WEATHER. 

on  an  ice  pitcher  on  any  hot  summer's  day. 
The  ice  chills  the  walls  of  the  pitcher  until 
the  air  in  contact  with  them  is  cooled  below  its 
dew-point  and  deposits  a  copious  dew  upon  the 
pitcher,  that  being  the  object  contact  with 
which  causes  the  air  to  cool. 

Dew  "  falls  "  when  the  air  is  calm  and  the 
sky  clear.  It  is  most  likely  to  fall,  and  is  most 
copious,  at  about  daybreak,  which  is  the  coldest 
and  calmest  part  of  the  day ;  but  it  may  begin 
before  sunset  the  evening  before.  It  can  not 
occur  where  the  sun's  rays  have  free  access,  for 
they  heat  the  solid  objects  until  they  are 
warmer  than  the  air ;  nor  can  it  occur  unless 
there  is  enough  moisture  in  the  air  to  give  a 
dew-point  above  the  temperature  of  the  bodies 
chilled. 

Hoarfrost  is  simply  dew  deposited  at  tem- 
peratures below  freezing.  It  is  formed  under 
conditions  otherwise  the  same  as  dew,  but,  un- 
like the  latter,  the  deposit  can  be  made  in  windy 
weather.  When  a  very  moist  air  sweeps  across 
small  bodies,  such  as  branches  of  trees  and  elec- 
tric wires  which  are  below  the  freezing  point, 
the  hoarfrost  may  continue  to  be  deposited  on 
them  until  they  become  so  loaded  as  to  be 
broken  down.  A  familiar  illustration  of  the 
formation  of  hoarfrost  is  that  to  be  seen  on  the 


DEW,   FOG,   AND  CLOUD.  75 

window  panes  in  winter.  The  air  of  the  room 
has  a  higher  dew-point  than  the  temperature  of 
the  panes  of  glass,  and  the  little  crystals  of  frost 
are  therefore  deposited  on  them.  These  crys- 
tals are  flat  and  applied  closely  to  the  pane, 
because  the  chilled  air  extends  but  a  very  small 
distance  from  the  pane.  The  flowery  patterns 
are  due  to  the  laws  of  crystallization  of  water ; 
they  are  also  seen  in  the  hoarfrost,  and  can  be 
found  in  ice  when  it  is  carefully  and  slowly 
melted  in  such  a  way  as  to  let  the  compacted 
crystals  free  themselves  from  each  other. 

With  the  dew  and  hoarfrost,  the  free  sur- 
face on  which  the  condensation  can  be  made  is 
easy  to  find,  but  in  the  free  air,  where  fog  and 
cloud  are  formed,  such  surfaces  are  not  visible. 
Still,  the  constant  deposit  of  dust  in  quiet 
places  shows  that  the  air  must  contain  innu- 
merable minute  particles  which  float,  or  slowly 
settle,  in  it.  And  these  can  be  made  visible 
by  admitting  a  beam  of  sunlight  in  a  darkened 
room  by  the  many  motes  in  its  pathway,  from 
which  the  light  is  reflected.  The  dust  in  the 
atmosphere  is  fairly  universal,  for  it  is  even 
found  deposited  on  the  glaciers  in  the  interior 
of  Greenland. 

Besides  these  particles,  which  can  be  ren- 
dered visible  by  a  beam  of  light,  and  are  rela- 


76  ABOUT  THE  WEATHER. 

tively  large  and  coarse,  observation  and  experi- 
ment has  proved  that  there  are  many  minute 
living  germs  floating  freely  about  in  the  atmos- 
phere. They  are  so  numerous,  indeed,  that 
only  by  the  most  careful  and  exacting  clean- 
liness can  they  be  kept  out  of  such  places  as 
wounds,  where  they  may  do  much  harm. 

There  is  yet  another  and  very  abundant 
source  for  particles  in  the  air  which  appear  to 
be  still  more  minute.  Most  solids  when  warm 
give  off  many  extremely  minute  portions  of  their 
substance,  and  some,  as  sulphur,  give  them  off 
in  great  numbers.  When  any  object  is  burned 
many  of  these  ascend  into  the  air.  The  exist- 
ence of  such  particles  gives  rise  to  a  phenom- 
enon of  light  called  diffraction,  which  consists 
of  the  turning  aside  of  a  beam  of  light  and 
separating  it  into  the  prismatic  rays  of  which 
it  is  composed  as  it  passes  the  edges  of  opaque 
bodies,  causing  the  appearance  of  fringes  of 
different  colors,  and  their  presence  enables 
clouds  or  fog  to  be  easily  formed.  There  has 
been  a  recent  illustration  of  the  great  quan- 
tity of  these  particles  which  may  be  poured 
out  into  the  air  during  volcanic  eruptions. 

In  1883  a  small  volcano  in  the  Straits  of 
Sunda  blew  up  with  a  violent  outburst.  It 
caused  the  death  of  scores  of  thousands  of 


DEW,   FOG,   AND  CLOUD.  77 

people,  created  an  enormous  wave  of  water 
which  traveled  far,  made  a  wave  of  air  which 
went  around  the  world  several  times,  and  it 
poured  out  such  an  amount  of  pumice  that  great 
quantities  floated  away  in  extensive  fields  to  so 
distant  a  place  as  the  Cape  of  Good  Hope.  But 
the  feature  of  especial  interest  here  is  that  the 
volcano  threw  out  into  the  air  such  enormous 
quantities  of  the  minute  particles  above  men- 
tioned that  they  spread  all  over  the  earth,  ex- 
cept to  high  latitudes,  and  by  diffraction  gave 
for  months  an  unusual  splendor  to  the  sunsets. 

It  appears,  then,  that  there  are  plenty  of  mi- 
nute particles  in  the  air  to  afford  the  nucleus  for 
the  droplets  or  crystals  of  cloud  and  fog.  The 
question  arises,  How  are  they  suspended  in 
the  air  ?  Water,  whether  as  a  liquid  or  in  crys- 
tals, is  always  heavier  than  air.  How  is  it, 
then,  that  the  fog  is  kept  suspended  overhead 
for  hours,  and  the  clouds  float  high  above  the 
earth  for  days  together  ? 

There  are  two  true,  and  yet  different,  an- 
swers to  this  question.  The  first  is  that  the 
droplets,  and  crystals  as  well,  are  not  suspended 
but  do  actually  fall  and  must  fall.  In  no  case  do 
they  stand  still,  but  they  fall  slowly  because  the 
air  offers  resistance  to  bodies  passing  through 
it.  This  resistance  increases  with  the  velocity, 


78  ABOUT  THE  WEATHER. 

of  the  falling  body,  but  at  a  faster  rate,  and 
sooner  or  later  puts  an  end  to  any  increase  in 
velocity.  After  that  the  body  falls  uniformly. 
The  smaller  the  body  is,  the  sooner  this  takes 
place,  and  in  the  case  of  the  minute  droplets  it 
comes  so  soon  that  their  rate  of  falling  is  only  a 
few  feet,  or  even  a  few  inches,  per  hour.  They 
fall  so  slowly  that  the  effect  is  much  the  same 
as  if  they  stood  still.  Even  the  relatively 
larger  raindrop  or  snowflake  is  not  permitted 
to  fall  very  fast. 

The  second  answer  to  the  question  is  that 
the  cloud  or  fog  marks  out  a  space  in  which 
the  temperature  is  below  the  dew-point,  and 
that  elsewhere  the  temperature  is  above  the 
dew-point.  Within  the  space  marked  out  by 
cloud  or  fog  condensation  can  take  place  ;  out- 
side of  it  this  can  not  take  place,  because  tem- 
perature and  humidity  are  not  right  for  it. 
Meantime,  inside  this  space  the  droplets  of  a 
cloud  fall  slowly,  and  some  of  them  must  pass 
out  of  it.  They  are  then  evaporated  and  dis- 
appear, thus  preserving  intact  the  bottom  of 
the  cloud. 

By  remembering  that  a  cloud  represents 
only  a  condition,  a  certain  relation  between 
temperature  and  humidity,  we  can  understand 
how  clouds  can  travel  so  fast.  One  sometimes 


DEW,   FOG,   AND  CLOUD.  79 

sees  them  overspread  the  sky  in  a  few  minutes, 
extending  themselves  at  the  rate  of  perhaps  a 
hundred  miles  an  hour.  It  is  the  condition 
that  extends  itself,  and  this  does  not  necessarily 
mean  the  bodily  motion  of  the  cloud  ;  the  chill- 
ing of  the  air  below  the  dew-point  at  that 
height  at  which  the  cloud  appears  is  what 
travels,  and  for  this  a  movement  of  the  air  is 
not  really  necessary. 

A  fog  is  a  cloud  at  the  ground,  and  a  cloud 
is  a  fog  high  up  in  the  air.  If  one  sees  a  cloud 
about  the  top  of  a  mountain  and  climbs  up 
to  it,  it  always  proves  to  be  a  fog.  The  con- 
ditions are  very  much  the  same  for  both,  but 
fogs  are  more  distinctly  diurnal — that  is,  more 
dependent  on  the  time  of  day.  Both  cloud  and 
fog  are  produced  by  cooling  the  air  below  the 
dew-point,  or  forcing  the  moisture  into  the  air 
until  super-saturated.  The  latter  is  the  process 
by  which  a  teakettle  or  locomotive  makes 
clouds  or  fogs  on  a  small  scale.  The  way  in 
which  fog  is  formed  in  Nature  is  by  chilling 
the  air  by  nocturnal  radiation  or  by  mixture 
with  cooler  air.  The  chief  way  in  which 
clouds  are  formed  is  by  ascending  currents  of 
air. 

The  method  employed  in  ascertaining  the 
heights  of  clouds  is  the  same  used  for  obtain- 


80 


ABOUT  THE  WEATHER. 


ing  the  distance  of  inaccessible  objects  —  such, 
for  example,  as  the  peaks  of  high  mountains. 
Use  is  made  of  the  triangle,  and  the  method 
is  called  triangulation.  Observers  at  A  and  B 
observe  the  same  point  G  on  the  cloud  and 
note  the  angles  CA  B  and  C  B  A.  The  dis- 
tance A  B  is  measured,  and  with  these  three 


.  • 


FIG.  14. — Finding  the  height  of  clouds.    A  little  practical  geome- 
try.    It  is  better  if  cameras  are  used  instead  of  theodolites. 

parts  of  the  triangle  the  length  of  the  other 
two  lines  can  be  obtained.  A  telephone  con- 
nection between  the  two  observers  enables 
them  to  fix  on  the  same  point  for  observation, 
and  if  they  take  photographs  the  problem  can 
be  worked  out  from  the  pictures.  A  series  of 
observations  or  photographs  gives  them  the 
movement  of  the  cloud. 


DEW,   FOG,   AND  CLOUD.  81 

Clouds  vary  in  height  from  two  hundred 
feet  to  ten  miles.  They  are  generally  from  a 
mile  to  five  miles  above  the  earth,  and  are  gen- 
erally higher  up  in  summer  than  they  are  in 
winter.  They  travel  at  rates  up  to  a  hundred 
miles  an  hour,  and  the  motion  averages  a  half 
more  in  winter  than  it  does  in  summer. 

There  are  three  fundamental  forms  of 
clouds :  cirrus,  cumulus,  and  stratus.  The  cir- 
rus, or  vail  cloud,  is  fine,  feathery,  of  a  silky 
texture  and  luster,  and  so  thin  that  stars  can 
easily  be  seen  through  it.  It  is  the  highest  of 
the  clouds,  being  from  three  to  ten  miles  above 
us.  These  heights  from  the  surface  of  the 
earth  were  determined  at  the  Blue  Hill  Meteoro- 
logical Observatory  near  Boston,  Mass.,  as  were 
the  measurement  of  all  other  heights  and  all 
rates  of  motion  here  given.  The  average  alti- 
tude overhead  for  cirrus  is  six  miles.  The 
color  of  cirrus  is  pearly,  and  its  luster  is  due 
to  the  fact  that  this  species  of  cloud  is  made  of 
ice  crystals.  Cirrus,  of  all  clouds,  moves  the 
most  rapidly ;  its  rate  averages  eighty  miles 
per  hour,  being  sixty-three  in  summer  and 
ninety-eight  in  winter. 

It  is  in  many  respects  the  most  interesting 
of  cloud  formations.  It  is  the  highest,  the  swift- 
est, the  thinnest,  and  the  only  one  generally 


ABOUT  THE  WEATHER. 


composed  of  ice  crystals.  It  is  the  usual  pre- 
cursor of  storms,  preceding  them  by  two  or 
three  days.  In  some  regions,  as  in  the  Pacific 
northwest,  it  is  a  rare  form.  On  the  other  hard, 


DEW,   FOG,   AND  CLOUD. 


83 


in  the  Northeastern  States  it  is  one  of  the  com- 
monest. It  is  the  form  that  shows  the  mackerel 
backs,  and  the  filly's  tail,  and  the  long  polar 
bands,  so  called,  which  stretch  across  the  sky 
from  some  point  in  the  horizon  to  a  corre- 


ABOUT  THE  WEATHER. 


spending  point  on  the  opposite  side.  In  all 
these  cases,  however,  it  is  in  progress  of  pass- 
age to  one  of  the  forms  which  follow.  In  the 
filly's  tail,  which  looks  like  a  wisp  of  fine  slen- 


DEW,   FOG,   AND  CLOUD.  85 

der  hairs,  it  has  taken  the  first  step  toward  the 
stratus  or  blanket  cloud,  and  in  the  polar  bands 
this  progress  is  still  farther  advanced.  The 
latter  has  gone  so  far  that  it  would  be  called 
cirro-stratus. 

The  mackerel  backs,  or  mackerel  sky,  and 
the  curdled,  fleecy  clouds  of  a  purer  white  form 
a  step  toward  the  cumulus,  and  are  called  cirro- 
cumulus;  these  are  white  balls,  arranged  in 
groups  or  rows. 

The  second  fundamental  cloud  form  is  the 
cumulus,  or  mountain  cloud.  It  is  very  wrhite 
above,  unless  tinted  with  gold  and  rose  color 
by  the  rising  or  the  setting  sun,  and  rounded, 
domed,  or  anvil-shaped.  It  is  the  thickest  of 
all  the  clouds,  standing  generally  isolated  from 
the  rest,  flat  and  darker  at  the  bottom.  When 
favorably  situated  it  casts  a  distinct  shadow, 
and  when  this  reaches  the  ground  it  enables  a 
single  observer  both  to  measure  its  velocity 
and  to  triangulate  for  its  height.  The  typical 
form  of  the  cumulus  is  a  cloud  of  medium  ele- 
vation, varying  in  horizontal  extent  from  two 
thousand  feet  to  two  and  a  half  miles.  Its 
thickness  averages  about  half  a  mile.  The 
usual  height  above  the  surface  of  the  earth  is 
one  mile.  The  cumulus  often  stands  still,  but 
when  it  does  travel  it  goes  at  the  rate  of  from 


86 


ABOUT  THE  WEATHER. 


DEW,   FOG,   AND  CLOUD.  87 

twenty  to  thirty  miles  an  hour,  averaging  for 
the  year  about  twenty-five  miles. 

This  very  characteristic  and  picturesque 
mass  of  vapor  is  a  warm-weather  cloud  form. 
It  is  most  common  in  hot  climates,  in  summer, 
and  during  the  warmer  part  of  the  day.  Its 
existence  is  due  to  the  ascent  of  the  air,  and 
the  growth  of  the  cloud  can  often  be  seen  if  it 
is  watched  through  a  telescope.  Even  with 
the  naked  eye  one  can  often  see  sudden  bulg- 
ings  and  twistings  about  the  rounded  protuber- 
ances. Sometimes  its  top  passes  off  into  a  cir- 
rus veil,  called  a  false  cirrus.  The  bottom  is 
occasionally  rent  by  winds,  in  which  case  the 
detached  parts  are  called  fracto-cumulus. 

The  stratus  or  blanket  cloud  is  the  third 
form.  It  is  darker  in  color  than  the  others,  a 
dark  gray,  with  sometimes  a  brownish  tinge. 
It  forms  a  layer  or  blanket  of  no  great  thick- 
ness, pretty  evenly  spread  over  a  larger  or 
smaller  portion  of  the  sky.  Seen  near  the  hori- 
zon, it  seems  but  a  band,  but  when  above  the 
observer  it  spreads  like  a  blanket,  thick  enough 
to  shut  out  the  sun  and  stars.  It  floats  near- 
est the  surface  of  the  earth  of  any  of  the  clouds, 
averaging  only  from  a  quarter  to  a  third  of  a 
mile  above  the  surface.  It  moves,  on  an  aver- 
age, at  a  velocity  of  about  twenty  miles  an 


88 


ABOUT  THE   WEATHER. 


hour;  being  sixteen  in   summer  and   twenty- 
three  in  winter. 

The  stratus  is  only  a  bank  of  fog  elevated 
above  our  heads.    It  is  the  cloud  of  melancholy 


DEW,   FOG,   AND  CLOUD. 


weather,  of  winter,  and  of  snow.    It  is  the  least 

interesting  and  least  picturesque  of  the  clouds. 

There  is  a  fourth  form  called  nimbus,  but 

its  only  character  is  that  rain  or  snow  is  falling 


n....0t 


90 


ABOUT  THE  WEATHER. 


DEW,   FOG,   AND  CLOUD.  91 

from  it,  and  this  does  not  really  distinguish 
it  from  the  others,  for  precipitation  occurs 
as  well  from  the  cumulus  and  stratus  and  from 
intermediate  forms. 

With  the  three  fundamental  forms  of  clouds 
well  in  mind  the  reader  can,  by  observation  of 
the  sky,  work  out  the  intermediate  forms  for 
himself.  This  is  the  more  necessary,  as  illus- 
trations can  not  bring  out  clearly  the  delicate 
forms  and  shades  of  clouds.  The  Weather 
Bureau,  whose  pictures  we  employ,  uses  ten 
names  for  cloud  forms.  These,  in  order  from 
the  highest  to  the  lowest,  are  the  cirrus,  cirro- 
stratus,  cirro-cumulus,  alto-stratus,  alto-cumulus, 
strato-cumulus,  cumulus,  cumulo-nimbus,  nim- 
bus, and  stratus. 

The  alto-stratus  is  a  thin,  high  stratus,  of  a 
gray  or  bluish  color,  lower  than  the  cirro- 
stratus,  and  not  fibrous  or  feathery.  It  is 
common,  and  is  described  by  the  name  which 
means  high  stratus. 

The  alto-cumulus  is  a  lower  and  denser 
cirro-cumulus.  It  is  a  dense,  white,  fleecy 
cloud,  composed  of  large  balls  in  flocks  or  rows, 
generally  close  together.  It  looks  like  a  large 
number  of  small,  high  cumuli  close  together. 


CHAPTEK  XII. 

PRECIPITATION  I     EAIN    AND    SNOW. 

THE  enormous  amount  of  work  done  by 
the  weather  can  be  best  understood  from  the 
rainfall.  If  a  hundredth  of  an  inch  of  rain 
falls — and  this  is  a  very  light  shower — it  will 
deliver  to  a  small  city  lot,  one  hundred  and 
thirty  gallons  of  water.  On  an  acre  the  fall 
will  be  a  full  ton,  and  over  a  square  mile  it  will 
be  the  enormous  quantity  of  seven  hundred  and 
twenty  tons  of  water.  More  than  ten  times  such 
an  amount  often  falls  in  an  hour,  and  it  all 
comes  from  the  height  of  about  half  a  mile. 
The  atmosphere  must  raise  this  amount  of 
water  to  this  height  and  keep  it  there  until  it 
is  to  fall  to  the  earth. 

It  is  raised  as  moisture,  but  falls  as  rain  or 
snow.  This  is  called  precipitation,  from  its 
exact  similarity  to  the  precipitation  in  the 
test  tube  of  the  chemist.  The  droplets  and 
ice  crystals  which  form  the  elements  of  the 
cloud  gradually  or  suddenly  grow  until  their 
weight  is  enough  to  bring  them  to  the  ground 

92 


PRECIPITATION:  RAIN  AND  SNOW.  93 

before  they  can  be  again  evaporated.  The  re- 
sistance which  the  air  offers  to  their  passage 
keeps  them  from  falling  too  fast.  The  drop  soon 
acquires  such  a  velocity  that  the  air  prevents  it 
from  going  any  faster.  The  larger  and  heavier 
the  drop  the  greater  is  the  speed  at  which  it 
falls,  but  it  is  never  great  enough  to  injure  us 
or  do  serious  damage  to  animals  or  plants. 
Were  it  not  for  the  resistance  of  the  air,  a 
drop  of  water,  notwithstanding  that  it  is  fluid, 
falling  from  the  height  of  half  a  mile  would 
be  as  dangerous  as  a  bullet.  The  swiftness 
and  force  with  which  a  projectile  travels  can 
be  made  sufficient  to  compensate  for  any  soft- 
ness or  yielding  quality  it  possesses.  A  candle 
when  fired  from  a  gun  will  pass  through  a 
board. 

Snowflakes  present  a  much  larger  surface 
to  the  resistance  of  the  air,  and  so  fall  more 
slowly  than  do  the  drops.  Hailstones  are 
made  under  conditions  which  permit  them  to 
attain  an  average  size  much  greater  than  that 
of  raindrops.  In  such  cases  they  may  fall  so 
rapidly  as  to  cause  much  destruction.  Scotch 
mist  is  a  form  of  precipitation  where  the  drops 
form  in  fog  and  are  very  small.  They  are 
large  enough  to  fall  visibly,  but  their  fall  is 
very  gentle. 


94  ABOUT  THE  WEATHER. 

The  intensity  of  a  rainfall  varies  from  the 
Scotch  mist  or  the  few  scattering  drops  from  a 
cumulus  on  a  summer  afternoon  to  a  rate  which 
may  give  a  depth  of  one  inch,  or  even  more,  in 
an  hour.  Such  heavy  rains  are  likely  to  cause 
inundations  in  the  country  and  an  overflowing 
of  the  sewers  in  the  city.  They  rarely  occur 
except  in  dry  climates ;  for  such  climates  are 
subject  to  the  double  disadvantage  of  having  a 
comparatively  small  annual  rainfall,  but  having 
that  fall  in  a  few  heavy  and  destructive  show- 
ers. The  heaviest  rainfall  recorded  in  the 
United  States  is  eighteen  inches  an  hour.  It 
occurred  in  southern  Idaho.  The  most  favor- 
able rain  for  all  purposes  is  a  gentle  and  long- 
continued  one,  and  that  is  the  most  likely  one 
to  fall  in  moist  climates. 

A  snowfall  is  equivalent  to  about  a  tenth 
of  its  depth  in  water — that  is,  a  snowfall  of  ten 
inches  would,  when  melted,  make  a  layer  of 
water  about  one  inch  deep.  A  deep  snowfall, 
though  injurious  to  traffic,  is  beneficial  to 
farmers.  While  it  lies  on  the  ground  it  pre- 
vents frost  from  penetrating  the  soil  and  it  pro- 
tects delicate  plants  from  freezing,  and  by  the 
cooling  it  produces  when  it  thaws  it  retards 
and  even  prevents  the  sudden  and  extreme 
changes  of  temperature  which  are  so  injurious 


PRECIPITATION :  RAIN  AND  SNOW. 


95 


to  life.  Moreover,  by  lying  late  in  the  spring 
it  keeps  plants  from  sprouting  too  early  and 
so  being  nipped  by  frost. 

The  snowflakes  are  of  varied  and  beautiful 
forms,  and,  in  accordance  with  the  laws  of 
crystallization  of  water,  are  sexanary  or  gov- 
erned by  the  number  six.  Six-rayed  stars  are 


FIG.  22. — Snow  crystals. 

the  most  common  form  of  snowflakes  in  mild 
weather,  and  the  enormous  flakes  that  some- 
times fall  at  the  beginning  or  end  of  winter 
will  be  found,  when  examined,  to  have  the  six 
rays,  each  branching.  As  the  weather  grows 
colder,  the  flakes  become  simpler  and  smaller, 
until" they  are  often  reduced  to  slender  six-sided 


96  ABOUT  THE   WEATHER. 

prisms  with  sharp  ends  or  to  flat  hexagonal 
scales.  The  needle-shaped  prisms  are  charac- 
teristic of  the  blizzard,  and  it  is  the  stinging 
which  they  cause  when  driven  against  the  skin 
by  a  high  wind  that  causes  most  of  the  suffer- 
ing in  these  dreadful  storms. 

Some  winter  fogs  are  made  up  of  ice  crys- 
tals instead  of  droplets.  They  are  practically 
cirrus  at  the  ground,  and  have  to  an  even 
higher  degree  the  translucent,  lustrous  appear- 
ance which  these  clouds  show.  They  are 
somewhat  iridescent  in  the  sunlight,  and  the 
effect  is  so  beautiful  and  striking  that  once 
seen  it  will  never  be  forgotten. 

The  measurement  of  the  precipitation  is 
very  simple  in  theory,  but  in  practice  accuracy 
is  very  difficult  to  attain.  The  essential  form 
of  a  rain-meter  is,  of  course,  some  sort  of  a 
cylindrical  receiver  exposed  to  the  rain ;  but 
rainfall  is  very  sensitive  to  gusts  of  wind,  wind- 
breaks, and  shelters.  A  can  placed  on  the  grass 
in  an  open  place  will  give  correct  measurements 
if  the  rain  fall  during  a  calm ;  but,  if  there  is 
any  wind,  eddies  will  form  around  and  carry 
the  raindrops  outside  of  it,  making  its  catch 
less  than  the  fall.  The  easiest  way  to  remedy 
this  is  to  sink  the  top  of  the  receiver  to  the 
level  of  the  ground. 


PRECIPITATION:  RAIN  AND  SNOW.  97 

The  total  amount  of  a  rainfall  usually  varies 
with  the  elevation  above  the  ground.  The  rain- 
drops continue  to  grow  during  their  fall  if,  as  is 
generally  the  case,  the  air  below  is  at  or  near  the 
dew-point.  The  drop  itself  forms  a  free  sur- 
face for  the  deposit  of  the  new  condensation, 
and  is,  moreover,  generally  cooler  than  the  air. 
In  dry  climates,  however,  the  opposite  may  be 
the  case,  and  the  drop  when  it  reaches  the 
ground  may  be  much  smaller  than  when  it  left 
the  cloud.  Indeed,  over  the  dry  plains  of  the 
Southwest  heavy  rains  are  often  seen  above 
which  never  reach  the  ground.  Strange  as  it 
may  appear,  it  is  no  unusual  thing  there  to  be 
under  a  shower  without  protection  and  yet  be 
perfectly  dry.  In  such  cases  the  raindrops  are 
completely  evaporated  by  the  layer  of  dry  air 
between  the  cloud  and  the  earth. 

It  is  commonly  thought  that  electricity  plays 
an  important  part  in  causing  weather.  It  is 
true  that  thunder  and  lightning  occur  in  many 
storms,  and  that  the  rainfall  is  often  heavier 
immediately  after  a  lightning  flash.  Rain  clouds 
undoubtedly  develop  a  strong  electric  tension, 
and  probably  electric  charges  on  the  surface  of 
the  drops  play  some  part  in  preventing  them 
from  growing  or  coalescing  when  they  come  in 
contact  with  each  other.  Just  how  far  these 


98  ABOUT  THE  WEATHER. 

things  are  necessary  and  how  the  work  is  done 
is  yet  uncertain.  So  far  as  actually  known,  the 
electric  phenomena  are  rather  a  result  of  the 
storm  than  a  cause.  That  electricity  plays  an 
important  part  in  the  economy  of  Nature  in 
general  is  beyond  a  doubt,  but  storms  often 
occur  with  but  faint  signs  of  electric  dis- 
turbance. 


CHAPTER  XIII. 

GENERAL   STORMS,    CYCLONES,   OR  LOWS. 

THE  most  remarkable  discovery  in  the  mod- 
ern study  of  the  weather  is  the  cyclone.  By 
this  word  is  meant,  not  necessarily  a  furious, 
destructive  storm,  but  only  a  circular  mass  of 
air — a  flat,  thin  vortex,  shaped  like  a  wafer  and 
having  a  system  of  internal  motions  of  its  own. 
These  motions  may  be  so  intense  as  to  be  very 
destructive,  but  nine  times  in  ten  the  cyclone 
is  a  very  gentle  creature — in  some  cases  so  gen- 
tle that,  though  it  passes  over  our  heads,  it  re- 
quires close  observation  and  delicate  instruments 
to  detect  it.  It  is  not  once  in  a  hundred  times 
that  a  cyclone  does  any  damage  to  man,  even 
when  we  count  an  occasional  stroke  of  light- 
ning. The  word  cyclone,  however,  is  so  fre- 
quently misunderstood  that  meteorologists  gen- 
erally use  others,  except  when  they  write  for 
their  fellow  students  of  the  weather.  They 
often  call  these  masses  of  air  general  storms, 
because  they  are  great  disturbances  of  the  at- 

99 


100  ABOUT  THE  WEATHER. 

mosphere,  and  therefore  are  storms  in  a  proper 
sense  of  the  word,  though  not  always  in  the 
popular  sense.  To  avoid  the  misapprehension 
that  the  word  storm  creates,  meteorologists 
often  use  the  word  "  low "  as  a  substitute  for 
"  cyclone  "  or  "  general  storm,"  because  it  has 
no  evil  popular  associations  with  it.  And  this 
word  is  appropriate,  for  it  expresses  the  state 
of  the  barometer  in  a  cyclone.  Besides,  this 
is  the  word  used  on  the  weather  map  to  mark 
the  center  of  the  cyclone.  (See  the  map  on 
page  101.) 

The  cyclone  appears  on  the  map  as  an  area 
of  low  pressure.  Around  the  center  the  iso- 
bars are  closed  up,  inclosing  an  area  or  island 
of  low  pressure.  The  inclosing  isobars  are 
usually  nearly  circular,  but  sometimes  oval  or 
even  irregularly  elongated.  When  they  are  so 
elongated  that  a  projection  or  trough  extends 
toward  the  equator,  they  are  likely  to  develop 
a  series  of  local  storms  of  great  interest,  but 
these  are  to  be  discussed  later.  The  more 
nearly  circular  the  isobars,  the  more  regular  is 
the  storm,  and  they  are  more  likely  to  be  cir- 
cular in  intense  storms  than  in  gentle  ones. 

At  the  center  itself  the  pressure  of  the  air 
is  the  lowest,  and  it  rises  as  one  passes  out 
from  this  point  in  any  direction.  The  isobaric 


GENERAL  STORMS,   CYCLONES,   OR  LOWS.     101 

lines  on  a  weather  map  are  much  like  the  pro- 
file lines  on  a  topographical  map,  and  many  of 


the  descriptive  words  of  the  former  are  taken 
from  the  latter.     The  low  represents  a  valley, 


102  ABOUT  THE  WEATHER. 

and  the  increase  of  pressure  in  all  directions 
from  it  represents  the  slope  up  from  the  val- 
ley. This  slope,  gentle  or  steep  at  first,  as  the 
low  is  gentle  or  intense,  is  always  gentlest 
on  the  advancing  or  eastern  side,  and  steepest 
on  the  rear  or  western  side.  The  change  in 
pressure  reaches  far  in  advance  of  the  other 
changes,  except  perhaps  that  of  the  clouds. 
The  barometer  often  begins  to  fall  two  or  three 
days  before  the  center  of  the  cyclone  comes 
on ;  hence  the  use  of  the  barometer  in  predict- 
ing the  weather. 

The  temperature  in  cyclones  changes  just 
the  other  way  from  the  pressure  of  the  air. 
When  the  pressure  rises  the  temperature  falls, 
and  when  the  pressure  falls  the  temperature 
rises.  There  is  thus  a  definite  relation  between 
the  isotherms  and  the  cyclone,  as  is  plainly 
shown  on  the  weather  map,  page  101.  The 
isotherms  rise  or  become  more  northern  in  the 
vicinity  of  the  low.  They  fall  or  become  more 
southern  in  the  neighborhood  of  a  high — the 
opposite  form  to  be  discussed  hereafter.  In 
general  the  temperature  is  higher  during  a  low 
or  cyclone  than  in  ordinary  weather,  and  de- 
cidedly higher  than  during  a  high.  This  is 
owing  partly  to  the  blanket  of  clouds  which 
cuts  off  radiation  and  so  prevents  the  loss  of 


GENERAL  STORMS,   CYCLONES,   OR  LOWS.     103 

heat  by  radiation  from  the  earth  to  the  sky, 
and  partly  to  the  condensation  of  moisture 
going  on  in  the  low.  In  great  and  intense 
cyclones,  as  typhoons  or  hurricanes,  this  heat 
is  described  as  being  so  great  as  to  be  stifling. 
Ordinary  gentle  cyclones  do  little  more  than 
to  equalize  the  extremes  of  day  and  night. 

The  winds  in  a  cyclone  are  of  especial  in- 
terest. They  were  the  key  to  the  discovery  of 
the  true  nature  of  the  cyclone.  If  the  winds 
on  the  specimen  map  are  carefully  compared, 
it  will  be  found  that  they  show  a  strong  tend- 
ency to  turn  toward  the  center  of  the  low, 
or  rather  a  little  to  the  right  of  the  center. 
The  winds  at  any  station  are  likely  to  be  more 
or  less  affected  by  the  character  of  the  country 
around  the  station.  For  instance,  at  Cincin- 
nati they  are  more  likely  to  be  recorded  as 
passing  up  or  down  the  valley  of  the  Ohio 
River  than  in  any  other  direction.  At  Denver 
they  are  more  likely  to  pass  north  or  south 
along  the  range  of  the  Rocky  Mountains  than 
east  or  west  across  them.  And  so  it  is  for 
many  stations.  The  local  conditions  are  likely 
to  give  special  direction  to  the  winds  at  the 
earth's  surface,  where  the  observations  must  be 
made. 

To  avoid  these  local  variations,  we  take  the 


104 


ABOUT  THE  WEATHER. 


average  directions  from  many  weather  maps, 
and  then  find  that  the  winds  about  a  cyclone 
center  are  arranged  as  shown  in  the  dia- 


gram    (Fig.    24).       They    flow    in     spirally 
toward  the   center,  and   the   direction  of  the 


GENERAL  STORMS,   CYCLONES,   OR  LOWS.     105 

whirl  is,  for  our  weather  maps,  always  the 
same. 

We  shall  now  have  to  define  the  direction 
of  a  whirl  or  turn  on  the  earth's  surface  in 
such  a  way  that  it  can  be  easily  recognized. 
This  is  not  only  desirable  in  order  to  give 
clear  ideas,  but  it  is  necessary  in  weather 
study,  because  it  fixes  the  succession  of  winds 
to  be  expected  when  a  storm  center  sweeps 
over  us.  To  fix  and  define  the  direction  of 
motion,  let  us  imagine  a  clock  or  watch  lying 
on  the  ground,  face  up.  Then,  if  the  wind 
move  or  turn  in  the  same  direction  as  the  clock 
hands  move,  we  may  call  it  clockwise  rotation : 
in  the  opposite  direction — that  is,  against  the 
hands  of  the  clock — contra-clockwise  ;  then  the 
whirl  in  the  diagram  is  contra-clockwise,  for 
it  passes  around  in  a  direction-  contrary  to  that 
of  the  hands  of  a  clock.  And  this  is  true 
for  all  great  whirls  in  the  northern  hemisphere. 
They  are  contra-clockwise. 

Great  whirls  in  the  southern  hemisphere 
turn  in  exactly  the  opposite  direction.  They 
are  clockwise.  That  the  directions  are  oppo- 
site in  the  two  hemispheres  of  the  earth  indi- 
cates that  they  are  due  to  some  guiding  prin- 
ciple which  is  in  an  opposed  direction  on  the 
two  sides  of  the  equator.  It  is  a  result  of 


106  ABOUT  THE  WEATHER. 

the  rotation  of  the  earth  on  its  axis,  and  it  is 
a  very  interesting  proof  that  the  earth  does 
turn.  The  explanation  of  how  the  rotation  of 
the  earth  causes  these  two  opposite  twists  is 
difficult,  and  requires  some  space.  It  is  so  im- 
portant that  it  will  be  made  the  subject  of  a 

separate  chapter. 
Here  it  is  enough 
to  know  that  the 
turning  is  contra- 
clockwise  in  the 
northern  hemi- 
sphere, and  clock- 
^  wise  in  the  south- 

PIG.  25. — Scheme  of  vertical  currents 

about  a  great  conflagration  in  the   c  ™n' 

open  air  on  a  calm  day.     They  are  J  t 

much   the   same  at  the  center  of  a 

great  general  storm,  only  more  ex-   that  the  air  about 

tensive. 

a  center  of  low 

pressure,  for  hundreds  of  miles  on  each  side, 
is  pouring  into  this  center,  and  that  it  is 
not  heaped  up  there,  for  the  pressure  at  the 
center  is  lower  than  elsewhere.  The  air  then 
must  pass  out  somewhere,  and  it  can  pass  out 
only  by  going  up.  The  condition  is  like  that 
often  seen  about  a  great  fire.  The  air  flows  in 
at  the  bottom  and  up  at  the  center,  as  in  the 
diagram  (Fig.  25).  And  so  we  have  the  foun- 
dation of  a  great  whirlpool  in  the  air,  something 


GENERAL  STORMS,   CYCLONES,   OR  LOWS. 

like  one  in  water,  but  with  the  axis  turned  up 
instead  of  down. 

The  air  which  rises  can  not,  however,  con- 
tinue to  do  so  indefinitely.  It  must  sooner  or 
later  flow  off  at  the  sides.  This  can  be  seen  in 
the  smoke  and  sparks  carried  with  it  in  the 
small  vortex  made  by  a  fire  in  the  open  air. 
In  the  great  natural  cyclone  this  outflow  can  be 
regularly  observed  in  clouds  and  on  mountains. 

If  the  currents  of  air  in  a  cyclone  could  be 
made  visible,  and  we  could  take  a  section  of  it 
through  the  center  and  look  at  it  from  the  side, 
it  would  look  like  the  diagram  of  Fig.  26. 


FIG.  26.  —  Probable  appearance  of  a  vertical  section  of  a  general 
storm,  cyclone,  or  low,  but  exaggerated  in  height.  It  is  five 
hundred  to  a  thousand  miles  across  and  only  a  mile  or  two 
high. 

We  are  to  think  of  it  as  of  the  form  of  a  wafer 
or  flat  round  cake,  but  the  diagram  is  too  thick 
for  the  breadth.  In  fact,  it  is  thirty  or  forty 
times  too  thick  ;  for  the  thickness  is  there  one 
thirtieth  of  the  breadth  or  diameter,  while  in 
Nature  it  is  only  about  one  one-thousandth. 
The  dotted  lines  in  the  figure  complete  the 
round  of  air.  They  have  not  been  observed, 
but  probably  exist  in  some  places  and  not  in 
others  around  the  margin. 


108  ABOUT  THE  WEATHER. 

The  outflowing  winds  above  have  also  a 
spiral  direction,  but  the  direction  being  out- 
ward, the  twist  is  the  opposite  of  that  of  the 
inflowing  winds  below.  Seen  from  above,  their 
turn  is  clockwise,  but  the  twist  is  much  greater 
than  that  of  the  inflowing  winds  below. 

Putting  all  these  things  together,  we  get 
the  following  important  rule  : 

If  an  air  whirl  is  large  enough  to  have  the 
earths  rotation  affect  it  appreciably,  then  in  the 
northern  hemisphere  the  inflowing  spirals  al- 
ways twist  contra-clockwise,  and  the  outflowing 
clockwise.  It  is  just  the  opposite  in  the  southern 
hemisphere. 

All  this  seems  complicated,  but  it  is  made 
simple  and  easy  by  a  model.  Take  a  sheet  of 
Bristol  board  and  draw  on  it  a  circle  with  a 
radius  of  six  inches.  Make  a  pinhole  through 
it  at  the  center,  and  cut  the  circle  out.  Then 
mark  one  side  "  Among  the  Clouds,"  and  draw 
on  it  as  many  gently  spiral  curves  sweeping 
toward  the  right  as  you  may  care  to  make, 
scattering  them  uniformly  around  the  center 
and  putting  an  arrowhead  on  the  outer  end  of 
each. 

Now  turn  the  circle  over,  and  on  the  other 
side  write  "  Among  Men,"  and  on  it  draw  in- 
flowing, sweeping  spirals,  contra-clockwise  or 


GENERAL  STORMS,   CYCLONES,   OR  LOWS.     109 

toward  -the  left,  and  put  an  arrowhead  on 
the  inner  end  of  each.  Then  imagine  the  up- 
flowing  winds  to  rise  at  and  near  the  center 
through  the  tissue  of  the  card. 

In  such  a  model  one  has  the  image  of  a 
cyclone  in  its  natural  proportions,  or  nearly  so. 
If  made  out  of  paper,  taking  two  hundred 
sheets  to  pile  up  an  inch  in  depth,  the  radius 
should  be  an  inch  and  a  quarter,  but  if  of  inch 
boards  the  radius  would  be  twenty  feet.  Such 
a  whirl  in  the  air  is  a  thin  disk  about  five 
hundred  times  as  broad  as  deep.  The  model 
could  be  made  a  little  more  complete  by  draw- 
ing on  it  across  the  center  a  heavy  straight 
arrow  to  indicate  the  direction  of  motion,  and 
then  trimming  down  the  rear  margin  a  little. 

A  general  criticism  of  the  model  is  that  its 
margins  are  too  well  defined.  In  Nature  the 
best  developed  part  of  a  cyclone  is  the  center. 
As  one  passes  out  from  that  the  vortex  grad- 
ually becomes  less  distinct. 

So  far  as  the  winds  are  concerned,  then,  a 
cyclone  is  a  thin  disk  of  air,  about  a  thousand 
miles  in  diameter  and  a  couple  of  miles  thick, 
lying  on  the  earth's  surface.  Within  this  space 
the  air  flows  in  along  the  ground,  up  around 
the  center  and  out  above,  and  always  with  a 
spiral  twist. 


CHAPTEK  XIV. 

THE    CYCLONE    AS    A    STEAM    ENGINE. 

THE  air  which  flows  into  the  cyclone  must 
be  more  or  less  moist.  The  more  moist  it  is 
the  more  intense  or  violent  will  be  the  storm. 
If  the  air  is  nearly  dry,  the  whirl  will  weaken 
and  soon  disappear.  It  is  the  moisture  that 
makes  it  active  and  keeps  it  going. 

The  temperature  generally  lowers  as  one 
ascends.  If  the  temperature  at  the  earth  is  at 
the  dew-point,  as  soon  as  the  air  begins  to  as- 
cend the  moisture  will  begin  to  condense,  and 
fog  will  be  the  result.  If  the  temperature  at 
the  earth  is  above  the  dew-point,  then  there  is 
a  layer  above  it  somewhere  which  is  at  the 
dew-point  of  the  surface  air.  When  the  air 
rises  it  must  sooner  or  later  reach  this  layer, 
and  when  it  does  so,  condensation  will  begin. 
This  layer  will  then  form  the  lower  surface  of 
a  cloud. 

When  the  rising  air  begins  to  condense  its 
moisture  the  latter  gives  out  heat,  and  this 
no 


THE  CYCLONE  AS  A  STEAM  ENGINE. 

warms  it  up  a  little.  This  is  not  enough  to 
evaporate  the  droplets  again,  but  it  is  enough 
to  make  the  air  warmer,  and  therefore  cause  it 
to  rise  higher.  The  rising  cools  it  again,  and 
this  condenses  some  more  of  its  moisture, 
warming  the  air,  causing  it  to  rise,  and  repeat- 
ing the  steps  of  the  process  just  described. 
And  this  process  is  repeated  as  long  as  there 
is  enough  moisture  to  condense,  or  the  move- 
ment of  the  air  is  still  upward.  It  thus  con- 
tinues and  extends  the  rise  of  the  air,  and 
makes  clouds  larger,  not  only  at  the  dew-point, 
but  for  some  distance  above  it. 

This  process  can  be  seen  occasionally  over 
a  pond  or  a  wet  swamp  on  a  hot,  calm  summer 
afternoon.  The  moisture  is  itself  lighter  than 
dry  air.  Besides,  it  catches  more  of  the  heat 
in  the  sun's  rays,  so  that  moist  air  warms  up 
faster  than  dry.  Hence  the  air  over  a  moist 
place  on  a  clear,  calm,  hot  afternoon  soon  be- 
comes warmer  and  lighter  than  the  surrounding 
air,  and  rises.  When  it  reaches  its  dew-point 
layer  above,  it  begins  to  form  a  pure  white 
cumulus  cloud,  and  this  is  likely  to  grow 
above  until  it  takes  the  form  of  a  hill  or  craggy 
mountain — flat  below,  rounded  or  peaked  above, 
with  projections  here  and  there,  especially  to- 
ward the  top.  With  an  opera  glass  or  small 


112 


ABOUT  THE   WEATHER. 


THE  CYCLONE  AS  A  STEAM  ENGINE.         H3 

telescope  its  process  of  growth  can  be  seen 
and  is  very  curious,  often  including  sudden 
bulgings  and  outbursts. 

The  whole  phenomenon  is  a  column  of 
rising  air  capped  by  a  small  cloud — a  small, 
slender  cyclone,  stationary,  and  of  a  very  sim- 
ple and  gentle  sort.  The  column  is  invisible ; 
nothing  of  it  can  be  seen  but  the  upper  end,  as 
defined  by  the  cap  of  cloud. 

As  the  sun  goes  toward  its  setting  and  the 
cool  of  the  evening  comes  on,  the  upward  mo- 
tion of  the  air  is  checked  and  finally  ceases. 
The  cloud  gradually  fades  away  and  disap- 
pears. If  the  wind  rises,  the  column  is  broken 
and  the  cloud  promptly  disappears. 

When  the  air  is  unusually  moist  and  the 
weather  hot  and  calm,  such  columns  may  form 
almost  anywhere.  Then  a  good  many  of  these 
cumuli  may  be  seen — small  and  scattered,  like 
fieeces  of  sheep  in  appearance,  resting  lazily  or 
drifting  gently  in  a  common  direction,  with 
some  slight  general  motion  of  the  air.  If  these 
cumuli  grow  during  the  day,  it  shows  that  the 
air  remains  moist,  or  is  getting  more  so,  and 
rain  is  likely  to  follow.  If  they  slowly  de- 
crease in  size  and  fade  away,  the  air  is  getting 
drier  and  no  rain  will  follow.  These  cloudlets 
have  long  been  used  as  a  weather  sign. 


ABOUT  THE  WEATHER. 

The  effect  oi  the  moisture  is  to  make  the 
cyclone  continue  and  grow.  Moisture  is  cool 
steam,  and  in  continuing  the  cyclone  it  does 
its  work  quite  as  truly  as  hot  steam  does  in  the 
steam  engine.  Hence  the  cyclone  is,  in  a  true 
sense,  a  steam  engine,  and  the  parallelism  be- 
tween it  and  an  ordinary  steam  engine  may 
be  carried  out  in  many  of  the  details.  The 
furnace  for  this  natural  steam  engine  is  the 
sun,  for  it  furnishes  the  heat  which  evaporates 
the  water  and  forms  that  state  of  steam  which 
we  call  moisture  or  the  humidity  of  the  air. 
This  furnace  runs  in  common  all  the  cyclones 
on  the  earth  at  any  time — and  there  are  many, 
perhaps  a  dozen  or  a  score.  The  boiler  is  the 
surface  of  the  earth,  where  the  evaporation 
goes  on.  The  conductor  for  the  moisture  is  the 
atmosphere,  which  carries  it  off  to  the  place 
where  it  is  condensed.  More  precisely,  the 
conductor  for  a  cyclone  is  the  column  of  rising 
air  near  its  center.  The  condenser  is  in  the 
cloud  layer,  and  it  is  here  that  the  energy  of  the 
moisture  is  applied.  The  work  is  that  of  mak- 
ing the  air  rise  and  of  continuing  the  cyclone. 

The  cloud  cap  of  a  cyclone  is  a  very  inter- 
esting structure.  Its  form,  as  seen  from  the 
side,  is  shown  in  Fig.  28,  where  the  great  arrow 
A  shows  the  direction  in  which  it  is  moving. 


THE  CYCLONE  AS  A  STEAM  ENGINE. 


115 


The  height  of  the  cyclone  as  compared  with 
the  breadth  is,  of  course,  very  much  exagger- 
ated, and  the  upper  surface  of  the  cap  is  not 
known  as  a  whole.  Hence  the  diagram  is 
closed  above  with  a  dotted  line.  The  dotted 
arrow  lines  below  indicate  the  invisible  inflow- 
ing and  upflowing  air  currents. 

The  advancing  edge  of  the  cloud  cap  is  cir- 
rus and  cirro-stratus,  and  is  very  thin.     It  ex 


FIG.  28. — Section  of  a  cyclone  at  the  center  and  through  the  axis, 
showing  the  cloud  cap,  the  inflowing  winds,  R,  and  the  direc- 
tion of  motion,  A.  Note  that  the  cloud  extends  farther  in 
front  than  to  the  rear. 

tends  out  a  day  or  two  in  advance  of  the  cen- 
ter, and  may  be  seen  thrusting  up  its  long  pin- 
ions in  the  west  long  before  there  is  any  other 
indication  of  the  approaching  low  except  by 
the  barometer.  Farther  back  the  cirrus  sinks 
and  passes  gradually  into  the  heavy  and  denser 
forms  of  the  center — compacted  cumuli,  from 
the  bases  of  which  rain  may  fall. 
The  change  in  cloudiness  behinc 


116  ABOUT  THE  WEATHER. 

is  in  reverse  order,  but  is  more  rapid.  The 
outer  cirrus  is  much  higher  than  the  other 
clouds,  and  the  lowest  cloud  is  at  the  center. 
If  we  could  see  an  entire  low  at  one  glance,  the 
side  view  would  be  curiously  like  a  broad,  very 
flat  toadstool,  of  which  the  stem  would  be  the 
column  of  ascending  winds, 

The  rain  comes  on  near  the  center  of  the 
cyclone,  but  rather  in  front  than  behind.  In 
the  diagram  it  would  be  from  the  clouds  above 
R.  At  this  point  the  rain  would  be  heaviest, 
and  might  come  down  in  torrents.  Around 
this  it  would  be  lighter,  and  generally  at  no 
great  distance  light  and  gentle.  It  extends 
farther  in  front  than  to  the  rear.  Snow  falls 
more  generally  from  the  under  surface  of  a 
cyclone  cap  than  does  rain,  and  about  the  R 
the  flakes  are  larger  and  softer. 

All  these  features  vary  with  the  intensity 
of  the  storm,  and  the  more  the  moisture  and  the 
greater  the  heat  the  greater  the  storm.  A  com- 
mon, fairly  developed  cyclone  gives  cloudiness 
for  three  days  or  so,  fresh  wind  and  rain  for 
several  hours.  Many  cyclones  pass  over  which 
give  only  gentle  airs  and  light  rains.  A  few 
have  no  rain,  and  some  but  little  cloud.  Very 
rarely  an  intense  cyclone,  a  hurricane,  gives  vio- 
lent winds,  dense  cloud,  and  torrential  rain. 


CHAPTER  XV. 

CYCLONES    TRAVEL    EASTWARD. 

THE  way  cyclones  begin  is  not  well  known. 
Sometimes  they  start  up  in  a  region  of  even 
pressure  and  great  heat  covering  a  large  terri- 
tory. This  corresponds  to  the  little  pond  cu- 
mulus mentioned  in  the  last  chapter.  The  the- 
ory is  that  the  warming  of  the  air  goes  on  for 
some  days  until  something  starts  an  uprush ; 
this  then  goes  on  of  itself  on  a  grand  scale,  and 
the  cyclone  begins.  This  mode  of  origin  oc- 
curs oftenest  on  the  ocean  and  in  the  tropics. 
Perhaps  the  tropical  hurricanes  originate  in 
this  way. 

Another  way  may  be  when  a  large  land 
area  is  covered  with  moist  air  and  becomes 
heated.  Then  trees,  rocks,  buildings,  any  pro- 
jections capable  of  warming  up  the  air  in  con- 
tact with  them,  start  a  series  of  small  rising 
currents,  each  capped  with  cloud,  and  the  con- 
ditions are  those  of  the  fleecy  signs  of  rain  of 
the  last  chapter.  If  the  rising  air  increases, 

117 


118  ABOUT  THE  WEATHER. 

and  the  clouds  grow,  one,  because  of  favoring 
circumstances,  finally  becomes  larger  than  the 
rest,  controls  them,  and  in  the  end  absorbs  them 
by  drawing  in  the  air  that  fed  them.  This 
larger  one  becomes  the  cyclone  which,  no  longer 
content  with  its  birthplace,  starts  off  on  its 
eastward  journey  to  its  final  destruction  in  the 
high  north  or  over  some  great  arid  expanse. 

New  lows  are  also  sometimes  formed  from 
the  remains  of  old  ones,  and  even  the  anti 
cyclones,  or  downpours  of  air,  sometimes  favor 
the  formation  of  cyclones  ;  and  the  tumult- 
uous rush  of  the  anti-trade  winds  high  up  in 
the  air  may  sometimes  aid.  But  the  complete 
account  of  the  birth  of  a  genuine  cyclone  has 
not  yet  been  made  out.  Though  cyclones  often 
spring  into  existence  before  our  eyes  on  the 
weather  map,  we  can  as  yet  do  little  but  sug- 
gest some  of  the  conditions  which  may  aid  the 
process. 

Once  formed,  the  cyclone,  if  in  the  temper- 
ate zones,  starts  on  a  journey  eastward.  The 
ordinary  paths  in  North  America  lie  across  the 
Northern  States,  but  there  are  many  variations 
in  the  path,  and  these  are  fairly  uniform  in 
themselves.  They  may  be  taken  as  branches 
of  the  principal  path,  and  as  such  they  are  rep- 
resented on  the  map. 


CYCLONES  TRAVEL  EASTWARD.  119 

The  main  traveled  road  of  the  cyclone 
centers  is  A.  It  passes  directly  from  the 
Great  Lakes  to  the  Atlantic  over  Michigan, 
Ontario,  New  York,  and  New  England ;  that 
is,  the  centers  on  the  average  take  this  path, 
while  the  storm  itself  extends  to  a  long  dis- 
tance to  the  north  and  to  the  south.  The 


FIG.  29. — The   course  of  a  cyclone  across  the  United  States  of 
America. 

branch  from  the  north  is  a  very  common  one, 
and  is  itself  branched  above  S.  The  path  of 
storms  in  the  wild  and  mountainous  regions 
west  of  this  branch  is  not  well  known,  but  it 
is  probable  that  the  most  of  the  lows  cross  the 
mountains  instead  of  coming  down  from  the 
polar  regions  along  their  eastern  slope.  The 


120  ABOUT  THE  WEATHER. 

branch  C  is  that  on  which  storms  come  directly 
from  the  Pacific.  These  are  not  very  common, 
and  are  shut  off  completely  during  the  long 
dry  summer  of  that  coast.  The  storms  of  path 
D  are  generally  not  strong,  nor  are  they  numer- 
ous on  any  of  the  southern  branches. 

Those  of  branch  E  are  rare,  but  bring  soft, 
mild  weather  even  in  the  cooler  seasons.  The 
path  F  is  that  of  the  hurricanes  of  the  West 
Indies  which  come  on  only  in  the  autumn 
months;  they  sometimes  dip  farther  to  the 
west,  as  did  the  disastrous  Galveston  storm  of 
September,  1900. 

There  is  also  a  considerable  number  of 
storms  which  affect  our  northern  border,  while 
the  centers  remain  in  Canadian  territory. 

These  are  the  average  or  customary  paths 
of  storms  affecting  the  United  States.  Many 
cyclones  originate  in  the  States,  but  wherever 
they  start  they  are  likely  to  move  at  once  so 
as  to  join  the  caravan  on  the  regular  routes. 
And,  in  general,  a  cyclone  which  is  abnormal 
in  its  path  is  exceptional  in  its  weather.  It 
may  move  out  because  of  unusual  strength,  and 
in  that  case  it  is  much  more  severe.  Or  it  may 
leave  the  customary  paths  because  the  forces 
joining  to  make  it  are  weak  or  ill  assorted,  and 
in  this  case  it  is  weak  and  soon  dies. 


CYCLONES  TRAVEL  EASTWARD.  121 

The  cyclone  usually  takes  about  five  days 
to  go  from  the  Pacific  to  the  Atlantic  coast — 
a  speed  rather  less  than  that  of  an  express 
train.  Indeed,  the  train  east  from  Seattle  or 
Tacoma  would  outrun  the  storm  by  a  day  or 
two  in  coming  into  Boston.  General  storms 
are  often  a  little  delayed  by  mountain  ranges, 
and  they  hasten  a  little  as  they  approach  the 
Great  Lakes  or  the  Atlantic  Ocean.  It  is  in- 
teresting to  note  how  the  cyclones  direct  their 
course  to  the  Great  Lakes  when  they  rise 
to  the  westward  of  them.  This  is  probably 
because  these  lakes  furnish  them  with  the 
moisture  needed  to  keep  them  going.  The 
same  thing  applies  to  their  approach  to  the 
Atlantic ;  but  this  leaves  unexplained  the  fact 
that  they  leave  the  warmer  Pacific  Ocean  or 
the  Gulf  of  Mexico. 

The  general  storms  that  pass  on  to  the  Atlan- 
tic are  not  lost  there.  They  are  felt,  sometimes, 
in  a  very  boisterous  way  by  steamers  crossing 
the  Atlantic  to  and  from  Europe.  The  most 
direct  and  the  usual  route  of  the  great  trans- 
atlantic passenger  steamers  is  along  the  usual 
route  of  the  storms  for  the  most  of  its  length. 

The  Atlantic  storms  generally  swing  north, 
and,  following  the  Gulf  Stream,  disappear  in 
high  latitudes,  often  to  the  north  of  Scandina- 


122 


ABOUT   THE   WEATHER. 


via.  A  few  take  a  more  southern  route  and 
reach  the  shores  of  Europe,  from  France  to 
Scotland.  The  European  general  storms  usually 
come  from  farther  south,  and  have  never  been 
in  the  United  States.  They  come  up  from  lati- 


FIG.  30. — The  way  general  storms  cross  South  America. 

tudes  on  the  eastern  Atlantic — on  paths  corre- 
sponding, perhaps,  to  the  Z>,  E,  and  F  paths  of 
the  United  States. 

In  South  America  the  general  storms  strike 
the  Chilian  coast,  especially  the  southern   or 


CYCLONES  TRAVEL  EASTWARD.  123 

Patagonian  part.  They  then  pass  northeast- 
ward and  disappear  on  the  Atlantic  from  Bio 
Janeiro  to  Buenos  Ayres.  The  arrangement 
there  is  a  close  counterpart  to  that  of  North 
America,  except  as  it  is  changed  by  the  differ- 
ence in  the  form  and  breadth  of  the  continent. 
General  storms  are  also  common  in  Australasia, 
passing  eastward,  generally  to  the  south  of 
Australia. 

Cyclones  last  several  days,  sometimes  as 
long  as  a  fortnight.  The  most  of  the  American 
ones  disappear  in  high  latitudes  over  the  North 
Atlantic  or  polar  ocean  when  the  temperatures 
are  too  low  to  keep  up  the  necessary  supply  of 
moisture.  The  process  of  dying  consists  in  the 
slowing  up  of  the  ascending  current,  the  rise  of 
the  barometer,  the  disappearance  of  the  cloud 
cap,  and  the  slowing  of  the  motion  forward. 
The  cyclones  which  cross  Europe  disappear 
over  the  dry  plains  of  Russia  and  Siberia.  This 
is  due  not  to  the  cold,  but  to  the  dryness. 

Over  the  United  States  cyclones  usually 
succeed  in  reaching  the  Atlantic,  though  some- 
times the  low  fills  up  and  disappears  within 
the  range  of  the  weather  map.  Many  local  and 
special  reasons  are  given  for  this,  but  none  of 
general  significance.  The  energy  of  the  low  is 

sometimes  exhausted  even  when  there  seems  to 

10 


124  ABOUT  THE  WEATHER. 

be  plenty  of  fuel  for  it  in  the  form  of  sunshine, 
and  plenty  of  energy  in  a  high  humidity.  On 
the  other  hand,  it  sometimes  persists  over 
regions  that  are  half  desert,  and  the  intensity 
of  some  winter  storms  shows  that  a  high  tem- 
perature is  not  always  necessary.  In  fact,  our 
knowledge  of  the  history  of  cyclones,  of  their 
origin  and  destruction  especially,  is  very  in- 
complete, and  the  coming  generation  may  find 
abundance  to  do  in  questioning  these  instru- 
ments of  Nature. 

Between  the  place  where  they  begin  and 
where  they  end  they  invariably,  in  the  tem- 
perate zones,  describe  a  long  path  to  the  east- 
ward. Many  theories  have  been  proposed  to 
account  for  this  motion,  but  there  are  only 
two  which  appear  to  be  based  on  efficient 
causes. 

The  first  attributes  the  eastward  motion  to 
the  rotation  of  the  earth.  This  is  known  to  give 
rise  to  a  drift  westward  near  the  equator,  and 
eastward  in  the  temperate  zones.  The  way  in 
which  it  works  will  be  examined  in  Chapter 
XVII.  Here  it  is  enough  to  note  that  the 
effect  is  more  marked  at  some  distance  above 
the  earth,  and  can  be  plainly  seen  in  the  clouds. 
A  cyclone  extends  a  mile  or  two  up  into  the 
free  air,  and  would  therefore  be  submitted  to 


CYCLONES  TRAVEL  EASTWARD.  125 

this  eastward  drift,  and  more  strongly  at  the 
upper  end  of  its  axis.  An  indication  that  this 
is  the  case  appears  in  the  fact  that  the  axis  of  a 
cyclone  is  usually  at  a  slant,  and  the  upper  end 
is  directed  eastward. 

This  is  the  case  when  the  cyclone  is  carried 
along  on  the  upper  drift,  while  the  lower  end 
is  dragged  along  the  earth.  Mountains,  hills, 
forests,  even  those  artificial  roughnesses  called 
cities,  all  exert  a  friction  on  the  air  currents 
passing  over  them ;  they 
serve  as  a  brake  to  the 
motion  and  hold  the  air 
back. 

A  second  efficient 
cause  for  the  eastward 
motion  of  cyclones  is  to 
be  found  in  the  way 
these  whirls  are  perpetu- 

i        -ITT     i  1        J       FlG-    31.— To  show   how  the 

ated.        We  have  already        cyclones  or  general  storms 

±"U    j.    ±~\~' ~  ln  U,T   ±V»/-v        advance.     The  center  is  at 

seen  that  this  is  by  the      first  at  E  but  is  transferred 

condensation     of     moist-        gradually  to  F ,  then   to  a 

point  farther  east,  and  so  on. 

ure.  Now,  in  the  north- 
ern hemisphere  the  warmest,  and  hence  the 
moistest,  winds  start  from  farthest  south.  These 
are  the  winds  A  in  the  diagram  (Fig.  31). 
Those  from  the  east  (^)  would  be  next  in 
order  of  temperature  and  humidity.  Then 


126  ABOUT  THE  WEATHER. 

would  come  those  from  the  north  ((7),  and  last 
those  from  the  west. 

The  winds  from  the  south  curve  around 
and  actually  enter  the  .area  of  rising  currents 
on  the  eastern  side,  and  the  greatest  activity  in 
condensation  is  where  they  rise.  This  makes 
a  new  center  of  the  cyclone  to  the  eastward 
of  the  old,  or  the  center  is  transferred  from 
E  in  the  diagram  to  some  point,  f,  to  tbe 
eastward  of  it.  The  cyclone  is  then  east  of 
where  it  was,  or  it  has  progressed  eastward. 
When  established  at  JFihe  warmest  and  moist- 
est  portions  of  the  atmosphere  pour  in  and 
up  just  in  front  of  that,  making  a  new  cen 
ter,  and  a  corresponding  new  advance  to  the 
eastward.  This  process  is  repeated  as  long  as 
the  A  currents  of  air  are  warmer  and  moister; 
though,  for  ease  in  explaining,  I  have  spoken  of 
the  progress  of  the  cyclone  as  a  series  of  steps, 
it  is  really  continuous. 

Besides  the  motion  eastward,  the  cyclone 
also  has  some  north  and  south  motion.  It  rarely 
follows  a  parallel  of  latitude,  but  generally  has 
a  strong  northward  or  southward  element  in  its 
progress,  and  each  is  over  a  certain  territory; 
that  is,  all  drift  is  northward  in  one  region  and 
southward  in  another.  The  sidewise  drift  de- 
pends on  variations  in  the  motions  of  the  upper 


CYCLONES  TRAVEL  EASTWARD. 

air,  and  this  is  somewhat  affected  by  mountain 
ranges,  plains,  and  oceans. 

It  also  depends  on  the  way  the  warmer  and 
moister  air  enters  the  cyclone.  In  Fig.  "31, 
F  is  a  little  to  the  north  of  E^  because  the 
spiral  brings  the  inflowing  currents,  A,  around 
to  that  point  before  they  rise.  The  progress  of 
the  cyclone  is  then  a  little  north  of  east.  If  the 
spiral  A  were  less  steep,  F  would  be  farther 
south,  and  the  motion  might  be  east  or  south 
of  east.  If  the  spiral  were  steeper,  F  would  be 
carried  still  farther  to  the  north,  and  the  prog- 
ress would  be  northeast,  or  even  more  northerly 
than  that.  In  general,  the  more  intense  the 
storm,  the  more  likely  it  is  to  turn  toward  the 
poles. 

Combining  all  these  features  together,  the 
picture  the  reader  is  to  form  in  his  mind  is 
that  of  a  series  of  great  whirls  in  the  air  in  the 
temperate  zones,  all  sliding  rapidly  eastward 
over  the  earth's  surface,  with  a  tendency  some- 
times toward  the  equator,  but  more  often  toward 
the  poles.  Each  one  lasts  several  days.  They 
pass  over  us  at  intervals  of  a  few  days,  and 
this  keeps  everything  stirred  up  and  ventilated. 


CHAPTER  XYI. 

THE   WEATHER    BROUGHT   BY   THE   CYCLONE. 

WE  will  now  trace  out  the  weather  brought 
by  the  cyclone  and  the  succession  of  the  changes 
experienced  by  an  observer  as  the  great  whirl 
or  vortex  drifts  past  his  station.  It  will  take 
the  whirl  several  days  to  pass,  the  time  it  re- 
quires to  do  this  depending  on  its  size  and 
speed.  An  ordinary  gentle  general  storm 
affects  the  weather  for  four  or  five  days,  and 
controls  it  for  three  or  four. 

The  first  change  is  in  the  barometer  and  in 
the  clouds.  The  barometer  falls,  first  slowly, 
then  more  rapidly.  With  a  fall  of  a  quarter 
of  an  inch  the  clouds,  appearing  first  in  the 
west,  have  generally  reached  the  zenith ;  at 
about  three  fourths  of  an  inch  the  rain  comes 
on.  The  barometer  continues  to  fall  during  the 
rain,  and  does  not  stand  still  until  the  heaviest 
part  of  the  storm  is  past.  Then  it  begins  to 
rise,  and  the  rise  is  more  rapid  than  the  fall. 
Such  is  the  succession  when  the  storm  passes 

128 


THE  WEATHER  BROUGHT  BY  THE  C\  CLONE.  129 

centrally  over  the  observer.  If  it  passes  to  the 
north  or  to  the  south  the  change  in  the  ba- 
rometer is  of  the  same  character,  but  less  in 
amount.  The  reader  can  perhaps  picture  these 
changes  better  if  he  marks  on  his  cyclone  model, 
already  made,  the  successive  isobars,  and  then 
causes  the  model  to  move  slowly  over  some 
point  on  a  map. 

The  storm  tends  to  cut  off  extremes  of  tem- 
perature ;  it  makes  the  day  cooler  and  the  night 
warmer  than  they  usually  are  in  clear  weather, 
and  the  average  temperature  a  little  higher. 
As  the  cyclone  comes  on,  the  temperature  rises 
gradually  until  about  the  center  of  the  rain 
area.  As  the  center  passes  the  temperature 
again  falls,  and  the  fall  is  more  rapid  than  the 
rise.  The  place  of  greatest  warmth  is  a  little 
in  advance  of  the  place  of  lowest  pressure. 
The  temperature  after  the  storm  has  passed  is 
usually  lower  than  when  the  storm  was  com- 
ing on.  This  is  because  the  air  in  the  rear  of 
a  storm  has  come  down  from  the  north. 

The  succession  of  winds  is  the  most  curious 
and  interesting  of  all  the  phenomena  of  the 
passage  eastward  of  a  general  storm.  If  the 
reader  will  transfer  to  a  transparent  sheet  (a 
piece  of  isinglass  or  a  sheet  of  gelatin,  or  of 
tracing  or  oiled  paper)  the  scheme  of  surface 


130 


ABOUT  THE  WEATHER. 


winds  on  his  model,  and  pass  this  over  the  sta- 
tion according  to  directions,  he  will  get  a  much 
clearer  idea  of  the  succession  of  winds  we  are 
now  to  explain. 

As  the  cyclone  passes  over  the  station,  the 
winds  will  change  direction  (haul,  or  veer,  or 
back),  and  there  will  be  three  different  cases, 
according  to  the  direction  in  which  the  center 


PIG.  32. — The  succession  of  winds  as  a  general  storm  passes  over 
us.  If  we  are  at  Xl  it  reverses;  if  at  X 2  it  veers;  if  at  X3 
it  backs. 

of  the  cyclone  passes  over  the  station,  or  to  the 
south,  or  to  the  north  of  it.  The  three  cases 
are  marked  on  Fig.  32. 

CASE  1. — The  cyclone  passes  centrally  over 
the  station  of  the  observer.  Let  the  great  ar- 
row in  the  diagram  represent  the  direction  of 
motion  of  the  cyclone,  and  the  cross  marked  I 


THE   WEATHER  BROUGHT  BY  THE  CYCLONE.     131 

the  place  occupied  by  the  observer.  Then,  if 
the  system  of  winds  is  imagined  to  pass  gradu- 
ally over  station  1,  it  will  have  first  a  gentle 
southerly  wind;  this  will  gradually  change 
to  a  stronger  southeasterly,  then  to  a  stronger 
easterly  wind ;  when  the  center  is  over  the 
station  this  wind  will  cease  ;  there  will  be  a 
calm  while  the  rain  descends  and  the  center 
passes  over;  then  there  will  suddenly  come  a 
strong  wind  from  the  west,  followed  by  lighter 
northwesterly  and  then  gentle  northerly  airs. 
With  these  the  cyclone  is  past  and  the  storm 
ends.  The  noteworthy  feature  in  this  case  is 
that  the  wind  abruptly  and  completely  changes 
its  direction,  with  a  more  or  less  long  interval 
of  calm  between.  In  violent  storms  this  abrupt 
change  in  direction  of  the  prevailing  wind,  un- 
less it  is  expected  and  preparations  made  for 
it,  is  very  dangerous  to  shipping.  The  central 
calm  in  hurricanes  is  known  as  the  eye  of  the 
storm.  It  is  especially  noteworthy,  because 
while  the  sea  is  very  rough  there  is  no  wind  to 
steady  the  ship. 

CASE  2. — The  center  passes  to  the  north  of 
the  observer.  Here  the  wind  starts  in  from 
the  southeast  and  then  changes  gradually 
through  the  south,  southwest,  and  west,  end- 
ing in  the  northwest.  To  the  observer  it  grad- 


132  ABOUT  THE  WEATHER. 

ually  shifts  through  about  half  of  the  points 
of  the  compass.  In  making  these  changes  it 
passes  from  east  through  the  south  to  the  west, 
or  follows  the  sun  in  his  diurnal  course.  A 
shift  of  wind  with  the  sun  is  called  veering, 
so  that  in  Case  2  the  rule  is  that  the  wind 
veers. 

CASE  3. — The  center  passes  to  the  south  of 
the  observer.  The  wind  here  starts  in  from 
the  east  and  changes  through  the  northeast 
and  north  to  the  northwest.  Here  the  change 
in  direction  is  from  the  east  through  the  north 
to  the  west,  or  against  the  sun.  This  is  called 
the  backing  of  the  wind,  and  the  rule  for  Case 
3  is  that  the  wind  backs  while  the  storm  is 
passing. 

From  a  consideration  of  these  cases  we  may 
easily  deduce  a  rule  for  predicting  the  weather 
as  a  low  comes  on.  It  is  this :  If  the  wind 
veers,  the  storm  center  wrill  pass  to  the  north, 
and  if  it  backs,  to  the  south.  When  we  know 
the  course  of  the  center  it  is  possible  to  give 
greater  precision  to  the  prediction  of  the  de- 
tails of  the  coming  weather. 

By  studying  the  directions  of  the  inflowing 
currents  of  air  in  a  cyclone,  as  in  Fig.  32,  we 
may  deduce  a  general  rule  for  telling  the  direc- 
tion of  the  storm  center  from  the  observer  at 


THE   WEATHER  BROUGHT  BY  THE  CYCLONE.     133 

any  time.  This,  in  many  cases,  is  important— 
especially  for  seamen  in  heavy  storms,  for  it 
enables  them  to  lay  their  course  away  from 
the  storm.  Otherwise  they  might  be  running 
into  rather  than  out  of  it.  The  rule  was  first 
drawn  up  by  an  eminent  Dutch  scientist,  and 
is  therefore  called  after  him — Buys-Ballot's  law. 
It  is: 

Stand  with  your  back  to  the  wind,  and, 
in  the  northern  hemisphere,  the  storm  cen- 
ter is  in  front  of  you  and  toward  the  left 
hand. 

The  succession  of  clouds  and  occurrence  of 
rain  or  snow  have  already  been  noticed.  The 
clouds  begin  in  high,  thin  curves,  gradually 
thicken  and  descend,  and  become  thickest  and 
lowest  near  the  center.  They  disappear  in  the 
reverse  order.  The  clouds  come  on  in  about 
twice  the  time  in  which  they  disappear,  and 
in  the  rear  they  are  more  likely  to  be  broken 
up  with  patches  of  clear  sky  between  them. 
The  westerly  and  northerly  winds  that  fol- 
low the  storm  center  are  well  known  as  clear- 
ing winds,  while  the  easterly  and  southerly  are 
clouding  ones. 

Rain  is  heaviest  just  in  front  of  the  place 
of  lowest  barometer,  and  it  comes  to  an  end 
more  abruptly  than  it  begins.  Snow  generally 


134  ABOUT  THE  WEATHER. 

extends  farther  out  on  all  sides  from  the  point 
of  heaviest  precipitation,  and  in  cool  weather 
the  rain  in  front  is  likely  to  change  to  snow  in 
the  rear. 

Moisture  increases  as  the  storm  comes  on. 
It  often  has  a  bad  effect  on  people  who  are 
not  quite  well,  especially  on  those  subject  to 
toothache,  neuralgia,  or  rheumatism.  They 
will  begin  to  feel  their  pains  a  day  or  so  be- 
fore the  center  of  the  storm  comes  on. 

The  weather  of  a  brewing  storm  is  depress- 
ing, that  of  a  clearing  storm  tonic.  Even  ani- 
mals seem  oppressed  and  disturbed  by  the  in- 
creasing moisture.  They  appear  troubled  at 
the  prospect  of  a  storm,  but  become  more 
cheerful  and  gay  when  the  storm  has  passed. 
The  increasing  moisture  tightens  the  joints  of 
furniture,  and  makes  windows  stick  and  doors 
creak.  The  ascending  air  draws  the  gases  out 
of  drains,  and  the  heavy  air  from  the  soil, 
causing  bad  smells. 

Details  differ  greatly  with  the  intensity 
of  the  storm.  In  an  intense  storm  everything 
is  more  regular  and  symmetrical.  The  depres- 
sion of  the  barometer  is  deeper,  the  temperature 
is  higher,  the  clouds  denser  and  with  more  mo- 
tion among  them.  Especially  the  spirals  of  the 
wind  are  stiffened  and  become  steeper,  carrying 


THE   WEATHER  BROUGHT  BY  THE  CYCLONE.     135 

inflowing  air  farther  around  before  it  can 
center  and  rise.  The  feeling  of  oppressive- 
ness also  is  heightened,  and  in  an  approach- 
ing hurricane  becomes  so  great  as  to  be 
painful. 


CHAPTEK  XYIL 

EFFECTS    OF   THE   EARTH'S    ROTATION. 

THE  mechanical  effects  of  the  earth's  rota- 
tion on  its  axis  is  the  chief  guiding  influence 
to  air  in  motion.  A  complete  analysis  of  its 
effects  requires  special  knowledge  of  mechan- 
ics of  a  sort  possessed  only  by  students  of 
such  subjects.  It  is  abstruse  and  difficult. 
Only  the  general  results  can  be  here  given 
and  illustrated. 

The  first  question  that  arises  is  this :  Does 
the  air  fully  take  on  the  earth's  motion  of  rota- 
tion, or,  because  of  its  soft  and  yielding  nature, 
does  it  tend  to  fall  behind  the  earth  as  the 
water  on  the  turning  grindstone  goes  slower 
than  the  stone,  and  so  has  a  motion  backward  ? 
Observation  shows  that  the  first  is  the  case; 
the  air  has  taken  up  the  motion  of  the  earth 
and  moves  with  it  quite  as  evenly  and  perfectly 
as  do  the  oceans  or  the  solid  crust.  And  this 
will  continue  so  long  as  the  earth's  motion  is 
uniform  and  the  air  is  at  rest  relative  to  it. 

136 


EFFECTS  OF  THE  EARTH'S  ROTATION. 

If  the  earth  should  begin  to  turn  slower  or 
faster,  then  there  would  be  a  motion  in  the  air 
until  it  had  settled  down  to  the  new  motion  of 
the  earth.  Such  changes  do  not  take  place, 
or,  if  they  do,  it  is  with  extreme  slowness. 
Thus  the  rotation  of  the  earth  does  not  cause 
motion  in  air  at  rest.  It  is  only  when  air 
moves  that  the  earth's  rotation  affects  it. 

This  is  the  case  whatever  way  the  air 
moves,  whether  vertically  or  horizontally. 
What  is  true  of  air  in  motion  is  true  of  all 
other  motions  and  can  be  applied  to  anything. 
If  a  stone  is  dropped  down  the  shaft  of  a  deep 
mine  or  from  the  top  of  a  high  tower,  it  will 
fall  not  exactly  under  the  spot  from  which  it 
was  dropped,  but  a  little  to  the  east.  This  is 
because  the  top  of  the  tower  is  moving  through 
a  greater  circle,  and  hence  faster.  For  any- 
thing moving  upward  the  result  is  the  reverse, 
except  that  it  is  affected  by  the  friction  of  the 
air.  In  any  case  the  effect  in  vertical  motion  ip 
slight,  and  in  problems  of  the  weather  it  can 
be  neglected. 

The  important  case  is  that  of  a  body  mov- 
ing horizontally — that  is,  along  the  earth's  sur- 
face or  parallel  to  it.  The  effect  is  then  so  con- 
siderable as  to  be  seen  in  many  kinds  of  motion. 
It  is  a  guiding  principle  which  directs  to  some 


138  ABOUT  THE  WEATHER. 

degree  the  motions  of  waters  on  the  earth,  and 
really  controls  the  great  motions  of  the  at- 
mosphere as  to  the  direction  they  must  take. 
The  effect  may  be  stated  in  a  simple  rule  which 
is  of  great  interest  and  importance.  It  is  this  : 

In  the  case  of  any  body  in  horizontal  mo- 
tion, the  rotation  of  the  earth  causes  a  divergence 
toward  the  right  in  the  northern  and  toward  the 
left  in  the  southern  hemisphere. 

This  is  for  an  observer  who  stands  looking 
in  the  direction  in  which  the  body  is  moving 
when  it  moves  away  from  him ;  the  greater  the 
deviation  the  greater  the  velocity.  It  also 
increases  with  the  latitude.  It  is  greatest  at 
the  poles  and  nothing  at  the  equator. 

The  best  illustration  of  this  deviating  or 
guiding  influence  is  given  by  a  pendulum  hung 
free  to  turn  as  well  as  to  swing.  If  such  a 
pendulum  is  set  swinging,  it  will  be  found  to 
move  with  each  swing  toward  the  right — or  in 
a  clockwise  direction — and  this  it  will  keep  up 
as  long  as  it  swings.  At  the  pole  it  would 
complete  the  circle  in  twenty-four  hours.  In 
the  latitude  of  New  York  it  would  take  it 
about  thirty-seven  hours.  The  time  increases 
as  we  pass  from  pole  to  equator.  This  is 
called  the  Foucault  pendulum.  It  is  easily 
made  and  tried.  To  make  the  deviation  plainly 


EFFECTS  OF  THE  EARTH'S  ROTATION.        139 

visible  the  pendulum  should  be  at  least  thirty 
feet  long. 

The  deviation  can  be  detected  in  the  case 
of  any  rapidly  moving  body  when  the  motion 
is  of  such  a  sort  that  it  admits  of  minute  and 
precise  observation.  Cannon  balls  deviate  ap- 
preciably to  the  right,  and  railway  trains  show 
a  strong  tendency,  when  they  leave  the  track, 
to  do  so  on  the  right-hand  side.  Streams  are 
more  likely  to  eat  out  the  right-hand  bank  than 
the  left.  In  the  great  rivers  of  Siberia,  flow- 
ing for  hundreds  of  miles  through  open  plains 
in  high  latitudes,  the  right-hand  banks  are 
usually  steep,  and  are  so  continuously  eaten 
away  by  the  water  that  in  many  cases  vil- 
lage sites  must  be  moved  back.  On  the  other 
hand,  the  left  banks  are  low  and  flat — plains 
over  which  the  river  has  in  the  course  of  cen- 
turies shifted  farther  and  farther  toward  the 
right. 

The  effect  of  the  earth's  rotation  is  shown 
still  more  distinctly  in  the  great  ocean  cur- 
rents. Each  ocean  in  each  hemisphere  is  prac- 
tically one  great  whirl  In  very  slow  motion.  So 
far  as  the  confining  shores  permit,  the  diver- 
gence of  the  currents  making  these  whirls  is 
in  accordance  with  the  rule  just  laid  down  as 

to  the  effects  of  the  earth's  rotation.     A  simi- 
11 


140  ABOUT  THE  WEATHER. 

lar  though  still  slower  whirl  exists  in  each  of 
the  Great  Lakes. 

The  air  over  the  earth's  surface,  except  in 
high  latitudes,  is  in  a  great  double  vortex,  one 
for  each  hemisphere.  The  air  along  the  equator 
rises  because  of  the  heat  of  the  sun;  pours 
in  along  the  ocean  surface,  making  the  trade 
winds,  and  out  above  in  these  winds  of  the 
upper  air  called  the  anti-trades.  Each  vortex 
makes  a  great  ring  around  the  earth,  and  con- 
trols these  currents  of  air  which  help  to  make 
the  eastward  drift  of  cyclones.  The  trades 
deviate  toward  the  west  on  account  of  the 
rotation  of  the  earth  and  in  accordance  with 
the  rule,  and  for  the  same  reason  the  anti- 
trades toward  the  east. 

The  ocean  surfaces  in  each  hemisphere  are 
occupied  by  a  series  of  almost  stationary  centers 
of  high  and  low  pressure,  already  mentioned, 
and  the  winds  about  these  show  to  a  marked 
degree  the  same  influence. 

It  now  remains  to  show'  how  this  guiding  in- 
fluence of  the  earth's  rotation  gives  to  cyclones 
their  contra-clockwise  rotation.  Let  us  suppose 
that  G  in  the  diagram  is  the  center  of  a  cyclone 
where  the  air  is  ascending,  and  that  P  is  a 
particle  of  air  a  long  distance  off.  It  feels  the 
suction  effect  of  the  rising  at  G  and  tends  to 


EFFECTS  OF  THE  EARTH'S  ROTATION. 


pass  along  the  arrow  P  C.     It  would  do  so  if 

let  alone,  but  in  conies  the  controlling  power  of 

the  great  turn  of  the  earth  and  twists  it  out  of 

its    course    toward    the    right. 

That  brings  it  in  an  hour  to  the 

point  1.      Now  it  tends  to  pass 

in  along  the  arrow  1  C,  but  it  is 

twisted  again  toward  the  right, 

and   arrives   at    2,    and    so    on 

through  the  points  3,  4,  5.    And 

when  it  gets  in  to  the  center,  if  it 

could  look  back  over  its  course 

it  would   find   that,  instead   of 

going  straight  toward  its  center, 

it  had  followed  a  curved  path 

marked  by  P  1,  2,  3,  4,  5.     And 

this  curve  is  the  contra-clockwise 

spiral  so  important   in  northern  weather.     In 

southern  weather  the  twist  would  be  to  the  left, 

and  the  result  would  be  a  clockwise  spiral. 


FIG.  33.— The  way 
a  particle  of  air 
is  caused  to  take 
a  contra  -  clock- 
wise spiral  in  en- 
tering a  cyclone. 


CHAPTER  XYIII. 


COEEESPONDING  to  the  centers  or  low  pres- 
sure of  cyclones  on  the  weather  map  is  a  series 
of  centers  of  high  pressure,  or  anticyclones. 
They  are  so  called  because  they  are  the  op- 
posite of  the  cyclones  in  having  a  downward 
motion  of  the  air  while  the  latter  have  an 
upward  motion.  In  other  respects  they  are 
contrasted,  though  not  in  all  cases  Direct  oppo- 
sites.  That  in  the  anticyclone  the  air  de- 
scends is  shown  by  the  fact  that  it  flows  out  in 
all  directions  from  the  base,  and  this  outflow 
could  only  be  kept  up  by  a  supply  from  above. 
The  outflow  is  gentle  in  most  cases,  and  so 
must  the  downfall  be.  There  are  a  few  cases 
in  which  the  air  seems  to  descend  like  a  cata- 
ract, for  in  these  cases  it  is  bitterly  cold,  and  the 
air  flows  off  in  a  strong  wind.  Such  is  the 
case  of  the  blizzard,  to  be  discussed  hereafter. 
The  downflow  generally  is  so  gentle  that  it  is 
but  a  gradual  sinking. 

142 


ANTICYCLONES,   OR  HIGHS.  143 

Another  way  of  knowing  that  this  is  a 
downflow  of  air  is  by  the  higher  barometer.  A 
mass  of  air  descending  will  cause  a  pressure 
due  to  its  weight,  and  also  an  addition  due  to 
its  motion  downward.  These  two  effects  will 
be  added  together  in  the  way  the  barometer  is 
affected,  and  will  make  a  higher  pressure  than 
usual.  In  the  same  way  a  mass  of  air  ascend- 
ing will  make  a  pressure  due  to  its  weight 
less  the  effect  of  its  rising,  and  this  will  make 
an  effect  on  the  barometer  less  than  the  aver- 
age. Steady  and  continued  changes  in  the 
barometer  must  be  due  to  such  causes. 

The  air  pressure  over  a  high,  or  anticyclone, 
is  fairly  uniform  for  a  large  area.  The  space 
covered  by  an  anticyclone  is  nearly  always 
larger  than  that  covered  by  a  cyclone,  and  the 
pressure  is  nearly  the  same  throughout.  It  is 
often  higher  above  the  average  pressure  than 
the  cyclones  are  below  it. 

The  relation  to  the  temperature  is  more 
complicated  than  in  the  cyclone.  The  descend- 
ing air  is  of  course  colder,  for  it  comes  from 
the  colder  regions  above — the  regions  that  give 
the  cold  to  high  mountain  tops.  At  the  same 
time  clouds  are  absent,  and  there  is  no  such 
protection  from  the  sun's  rays  in  the  daytime 
nor  from  loss  of  heat  to  the  sky — which  is 


144  ABOUT  THE  WEATHER. 

always  so  cold  that  when  clear  it  will  take 
up  all  the  heat  that  is  sent  to  it.  The  result 
is  that  the  nights  are  decidedly  colder  in  anti- 
cyclonic  than  in  cyclonic  weather,  and  the  days 
are  decidedly  hotter.  The  weather  on  the 
whole  is  colder,  sometimes  very  much  colder ; 
but  the  contrast  between  day  and  night  is  also 
very  much  greater.  So  far  as  the  temperature 
is  concerned,  this  weather  is  not  so  easy  to  bear 
as  the  cyclonic  weather. 

The  winds  are  usually  very  gentle,  often 
hardly  appreciable,  especially  near  the  center 

of  the  area.  Farther  out 
a  system  of  winds  can 
be  traced  which  are  out- 
flowing and  are  gently 
spiral.  They  are  clock- 
wise and  correspond  to 
the  upper  winds  in  a 
cyclone.  So  far  as  the 
winds  are  concerned,  the 

FIG.  34.— Scheme  of  outflow-   o^t^vplrynp        rrmv        V»p 

ing  winds  from  a  high.  They  anticyclone       may 

are  less  curved  than  the  looked  on  as  a  large  and 

winds  flowing  into  a  low. 

gentle    cyclone    turned 

upside  down.  The  curvature  of  the  outflowing 
winds  is  sometimes  scarcely  perceptible.  As  a 
whole,  and  in  general,  the  high  is  a  calm  area, 
or  with  light  winds  only. 


ANTICYCLONES,   OR  HIGHS.  145 

The  air  of  the  anticyclone  is  generally  dry ; 
that  is,  drier  than  the  average  air.  The  relative 
humidity  is  low.  This  is  because  the  air  has 
settled  down  from  above  where  the  humidity  is 
small,  and  it  can  not  be  large  because  of  the 
coldness  there.  In  settling  down  it  has  forced 
its  way  into  denser  air.  Now,  the  condensation 
of  a  gas  always  makes  it  warmer.  Advantage 
can  be  taken  of  this  to  light  a  piece  of  punk  in 
a  tube  in  which  a  rapid  condensation  of  dry  air 
is  effected  by  driving  in  a  piston.  Probably 
some  ingenious  person  will  some  day  make  an 
everlasting  match,  without  the  use  of  the  dan- 
gerous phosphorus,  in  this  way. 

In  the  case  of  the  anticyclone  the  air  as 
it  settles  down  becomes  gradually  denser,  and 
hence  warmer,  and  the  humidity,  low  at  first, 
becomes  still  lower.  Clouds,  of  course,  can  not 
be  formed  under  these  conditions,  and  the 
great  anticyclone  is  clear  and  sunny  or  lighted 
by  the  stars.  There  can  also  be  no  rain  or 
snow,  and  so  the  anticyclone  adds  nothing  to 
the  natural  water  of  the  area  over  which  it 
passes  or  stands.  Its  dryness  makes  it  rather 
increase  the  evaporation,  and  so  tends  to 
aridity. 

We  have  just  spoken  of  the  standing  of 
the  high.  It  has  an  eastward  movement,  as 


146  ABOUT  THE   WEATHER. 

has  the  low,  but  in  the  former  it  is  slower  and 
more  uncertain,  and  less  definite  in  its  path. 
Besides,  it  is  likely  to  make  halts  at  favorite 
places,  sometimes  for  days  together  and  occa- 
sionally for  weeks.  One  of  its  favorite  halting 
places  is  over  the  valley  of  the  Cumberland 
and  surrounding  regions,  and  here  it  may  stay 
for  a  month  or  two.  Another  is  over  the 
great  interior  basin  of  the  West — Utah  and 
Nevada.  The  anticyclones  are  inclined  to  run 
to  the  south  of  the  cyclone  paths.  They  usu- 
ally come  on  from  the  West  to  the  lower  Ohio 
valley,  and  from  there  pass  a  little  to  the  south, 
leaving  the  coast  near  Cape  Hatteras. 

The  weather  of  a  high  or  anticyclone  can 
easily  be  guessed  from  that  which  precedes  it. 
It  is  calm  and  clear,  hot  in  the  day  and  cold  at 
night,  likely  to  be  frosty,  dry,  and  somewhat 
trying.  At  the  same  time  the  air  is  very  pure 
and  bracing.  It  makes  the  calm  and  sunny 
weather  which  everyone  prizes,  when  it  does 
not  last  too  long.  It  also  makes  the  weather 
of  the  long-continued  drought  so  injurious  to 
the  farmer.  The  untimely  and  destructive 
frosts  of  late  spring  and  early  summer  are 
almost  invariably  anticyclonic.  The  rapid 
passage  of  an  anticyclone  to  cyclonic  weather 
is  a  welcome  change.  The  long  delay  of  an 


ANTICYCLONES,  OR  HIGHS.  147 

anticyclone  over  any  place  brings  drought, 
nervousness,  and  distress.  The  cyclone  brings 
cloud  and  storm,  but  it  also  brings  the  welcome 
rain  and  keeps  the  air  well  ventilated  and 
sweet.  The  anticyclone  brings  bright,  sunny, 
tonic  weather ;  but  this  degenerates  into  dry, 
stagnant,  dusty  days,  and  dry  and  frosty  nights, 
if  it  lingers  too  long. 

When  the  anticyclone  comes  and  stays  in 
summer  it  brings  a  time  in  which  sunstrokes 
occur,  and  the  heat  becomes  intolerable,  espe- 
cially in  great  cities.  In  the  country  it  may 
cool  off  at  night,  but  in  the  city  the  thermom- 
eter remains  high,  because  the  pavements  and 
walls  of  the  buildings  get  so  heated  during  the 
day  that  they  give  out  heat  all  night.  Germs 
of  infection  then  develop  and  spread,  the  hos- 
pitals are  full,  and  death  reaps  a  rich  harvest. 
Even  in  the  country  the  springs  dry  up  and 
the  streams  evaporate  until  they  become  thick 
with  germs,  and  fevers  and  other  diseases 
result.  Such  weather  has  been  called  a  usiz- 
zard  "  —a  humorous  modification,  probably,  of 
its  opposite,  blizzard.  It  may  be  defined  as  a 
period  of  high-pressure  days  about  midsummer. 


CHAPTEE  XIX. 

BETWIXT-AND-BETWEEN    WEATHER. 

THOUGH  the  cyclone  and  anticyclone  are 
the  leaders  in  the  procession  of  the  weather 
eastward,  they  by  no  means  embrace  it  all. 
The  weather  map  of  the  United  States  has 
rarely  more  than  two  of  each  at  any  one  time 
Quite  frequently  there  is  but  one  center  of 
pressure,  and  not  very  infrequently  none,  or 
not  a  well-defined  one,  on  the  entire  map.  The 
weather,  then,  must  be  weather  other  than  the 
cyclone  or  anticyclone — betwixt-and-between 
weather,  intermediate  weather.  In  the  tropics 
this  can  hardly  be  called  intermediate  weather, 
for  little  of  the  cyclonic  or  anticyclonic  occurs 
there,  and  that  which  is  between  cyclones  here 
is  there  ordinary  weather.  As  one  passes  north 
the  centers  of  pressure  become  more  and  more 
common ;  at  least  over  the  North  American  con- 
tinent, until  a  latitude  of  about  45° — halfway 
to  the  pole — is  reached,  when  we  find  the  maxi- 
mum number.  Above  that  they  are  fewer,  at 

148 


BETWIXT-AND-BETWEEN  WEATHER.          149 

least  to  as  high  north  as  our  knowledge  ex- 
tends. The  "  betwixt-and-between  "  weather 
is  therefore  the  more  common  weather  in  the 
Southern  States,  and  especially  in  Florida  and 
in  the  Southwest.  It  is  also  more  prevalent 
through  the  drier  seasons  of  the  year. 

The  most  striking  and  noteworthy  inter- 
mediate weather  is  when  the  great  centers  of 
pressure  are  so  placed  with  reference  to  each 
other,  or  with  reference  to  the  irregularities  of 
the  earth's  surface,  or  to  the  currents  of  air 
at  some  distance  above  the  earth,  that  the  one 
aids  the  other.  The  commonest  case  is  that  of 
the  westerly  gales  which  sometimes  prevail  over 
a  large  part  of  the  States  for  two  or  three  days 
together.  They  usually  come  on  in  the  autumn 
or  winter,  but  may  prevail  at  other  seasons  of 
the  year.  These  gales  blow  over  an  area  sev- 
eral hundred  miles  across,  and  are  so  high  as  to 
be  dangerous  to  shipping ;  those  of  the  autumn 
are  especially  dangerous  and  destructive  on  the 
Great  Lakes.  Such  gales  usually  originate 
through  the  cooperation  of  a  low  with  a  high 
which  lies  to  the  west  of  it.  The  higher  winds 
above  thus  get  a  start  for  a  sweep  over  the 
earth,  and  when  this  is  once  begun  it  is  likely 
to  die  out  with  difficulty. 

When  an  anticyclone  lies  to  the  north  and 


BETWIXT-AND-BETWEEN  WEATHER. 

is  just  east  of  the  Rocky  Mountains,  and  espe- 
cially when  a  cyclone  lies  to  the  south  and  east 
of  the  anticyclone,  the  conditions  are  favorable 
for  conducting  a  polar  wind  far  to  the  south. 
Thus  arise  the  northers  of  Texas — high,  cold 
winds  which  sweep  down  from  the  north  with 
high  velocity  and  a  head  of  cloud,  dust,  and 
sand,  suddenly  changing  the  temperature  in 
Texas  from  almost  tropical  to  frigid.  The 
norther  can  be  seen  coming  from  a  long  dis- 
tance, and  its  approach  greatly  disturbs  animal 
life.  The  fall  of  temperature  is  very  rapid, 
and  a  high  north  wind  replaces  calm  or  gentle 
breezes  from  the  south. 

The  norther  occurs  in  winter,  and  is  very 
much  dreaded.  It  often  extends  down  over 
the  Gulf  of  Mexico,  making  tempestuous  winds 
in  the  western  part  of  that  body  of  water. 
Sometimes  it  goes  still  farther,  and,  crossing 
the  narrow  part  of  southern  Mexico  and  north- 
ern Central  America,  brings  high,  cool  winds 
over  to  the  Pacific  Ocean,  extending  nearly  to  the 
equator.  The  norther  is  one  of  the  most  injuri- 
ous features  of  weather  over  the  western  plains. 

Intermediate  weather  may  occur  in  other 
parts  of  the  United  States.  The  cold  wave 
is  an  extension  of  the  high  toward  the  east 
and  southeast.  Otherwise  it  is  like  the  norther. 


152  ABOUT  THE  WEATHER. 

bat  the  conditions  for  a  flow  of  polar  air 
toward  the  east  or  southeast  are  rarely  so 
favorable  as  toward  the  south.  Hence  the 
change  is  generally  not  so  fierce  and  the  wind 
not  so  high.  At  the  time  of  a  cold  wave  a 
well-marked  high  stands  in  the  northwest,  east 
of  the  mountains,  and  conducts  the  cold  upper 
and  northern  air  down  over  the  warmer  areas. 
The  sky  clears,  the  wind  is  high,  and  the  cold 
severe  for  the  season  of  the  year.  Cold  waves 
come  on  generally  in  autumn  and  winter,  and 
may  carry  a  frost  or  even  a  severe  freeze  down 
to  the  Gulf  of  Mexico,  and  in  rare  cases  well 
over  the  peninsula  of  Florida.  The  wind  lasts 
from  one  to  three  days,  and  then  the  high 
itself  comes  on,  bringing  calmer,  clear,  and  still 
colder  weather.  This  is  the  greatest  weather 
misfortune  that  occurs  to  the  Eastern,  and  espe- 
cially to  the  Gulf  States.  The  hurricane  itself, 
which  may  affect  the  Atlantic  coast  to  as  far 
north  as  Nantucket,  does  not  do  such  serious 
damage,  and  the  damage  it  does  is  more  easily 
repaired.  The  tornado  is  very  limited  in  its 
destruction  ;  besides,  it  does  not  extend  so  far 
east.  The  damage  done  by  the  cold  wave  in 
the  South  is  chiefly  that  of  freezing  delicate 
plants.  Orange  groves  subjected  to  this  severe 
weather  take  years  to  recover. 


BETWIXT-AND-BETWEEN  WEATHER.          153 

One  special  form  of  the  cold  wave  is  fortu- 
nately almost  always  much  more  confined  in 
its  area.  This  is  the  blizzard.  It  is  an  unusu- 
ally severely  cold  wave,  during  which  the  air 
is  filled  with  fine  snow  driven  before  the  high 
wind.  This  snow  consists  of  minute  sharp 
needles  of  ice,  and  is  so  abundant  that  it  shuts 
off  the  view,  and  so  irritating  when  it  strikes 
the  skin  or  is  breathed  that  it  soon  produces 
death  in  those  exposed  to  it — death  frequently 
preceded  by  madness  in  man  and  animals. 
Such  a  tempest  causes  great  destruction  among 
cattle,  and  the  only  security  from  it  is  to  have 
them  housed  before  it  begins.  So  distressing 
and  bewildering  is  this  storm  that  men  have 
been  known  to  get  lost  and  perish  in  passing 
between  the  house  and  the  barn.  The  bliz- 
zard is  a  winter  storm,  and  rarely  extends  be- 
yond the  northwestern  States  east  of  the 
mountains. 

Less  understood,  but  probably  due  to  simi- 
lar causes,  are  the  hot  winds  of  spring  and  sum- 
mer occurring  in  the  central  western  regions 
from  California  to  Kansas.  In  California  they 
are  northerly,  in  Kansas  southerly.  They  come 
on  suddenly,  and  are  so  hot  that  they  actually 
scorch  the  growing  crops  and  make  burns  on 
the  exposed  side  of  the  fruit.  The  hot  air  ap- 


154  ABOUT  THE  WEATHER. 

parently  passes  out  of  a  high,  intensely  heated 
region  over  some  extensive  arid  area — southern 
Idaho,  on  the  one  hand,  and  perhaps  Arizona 
or  New  Mexico  on  the  other.  Such  winds 
are  of  the  same  character  as  the  sirocco  of  the 
western  Mediterranean  region. 

From  the  nature  of  the  case  the  great  out- 
flows of  intermediate  weather  must  come  from 
the  anticyclone,  for  it  is  the  form  from  which 
the  wind  flows  away.  The  intermediate 
weather  of  cyclones  must  depend  on  inflows  or 
the  results  of  disturbances  on  the  margin  of 
the  great  indraft  of  the  low.  There  are  many 
such  inflows,  and  some  of  them  are  very  im- 
portant. They  are  generally  themselves  whirls, 
being  due  to  the  disturbance  of  a  great  whirl, 
but  a  few  are  apparently  of  different  character. 
For  instance,  a  sort  of  storm  of  rare  occurrence 
is  the  ribbon  storm,  where  a  high  wind  runs 
in  a  narrow  streak  without  appreciable  whirl. 
These  are  called  tornadoes,  but  they  are  not. 
They  can  be  distinguished  by  the  fact  that  the 
things  overthrown  by  them  are  not  thrown 
down  in  a  spiral  direction  that  can  be  recog- 
nized. Besides,  there  are  likely  to  be  several 
parallel  ribbon  storms  at  the  same  time  and 
not  far  apart,  a  thing  that  could  not  happen 
with  intense  whirls  like  tornadoes  any  more 


BETWIXT-AND-BETWEEN  WEATHER.         155 

than  one  could  have  several  whirlpools  close 
together  in  water. 

There  are  also  other  rare  and  little-known 
forms.  The  air  is  capable  of  containing  gusts  and 
whirls  of  many  sorts,  light  or  intense,  not  only 
at  the  surface  but  at  some  distance  above.  Bal- 
loonists  often  meet  narrow,  limited  winds  above 
the  earth's  surface,  and  the  confused  movements 
of  the  clouds  in  breeding  weather  show  how  va- 
ried the  motions  of  the  air  may  be.  The  differ- 
ent forms  have  not  yet  been  separated  complete- 
ly from  each  other ;  the  separation  is  difficult  be- 
cause one  form  passes  into  the  other.  There  are, 
however,  a  few  forms  so  distinct  and  so  interest- 
ing that  they  should  receive  separate  treatment. 

These  come  under  the  general  head  of  local 
storms,  as  opposed  to  the  general  storms  al- 
ready described.  They  are  small,  last  not  many 
hours,  and  travel  but  a  few  miles.  They  bring 
the  most  of  the  rain  in  the  tropics  and  in  sum- 
mer, and  may  be  in  connection  with  a  cyclone 
or  may  not.  With  us  a  connection  with  the  cy- 
clone can  be  generally  traced ;  in  the  Southern 
States  this  connection  is  rarer,  and  in  the  trop- 
ics very  rare.  They  may  be  due  even  to  local 
conditions,  and  their  paths  are,  in  the  gentler 
forms,  more  or  less  controlled  by  the  topogra- 
phy of  the  surface  of  the  earth  where  they  occur. 
12 


CHAPTEK  XX. 

TORNADOES    OR    INTENSE    LOCAL    WHIRLS. 

THE  tornado  is  an  intense  whirl  of  small 
dimensions.  The  central  destructive  part  is 
only  a  few  rods  wide,  and  the  entire  system  of 
winds  is  probably  only  a  mile  or  two  across. 
It  is  a  creature  of  a  few  hours  only,  and  not  of 
days  or  weeks  like  the  cyclone.  It  is  gener- 
ally a  sort  of  attendant  of  the  cyclone,  being 
developed  in  its  outskirts.  Hence  it  is  called 
a  secondary  whirl,  the  cyclone  itself  being  the 
primary. 

The  relations  of  tornado  to  cyclone  are  curi- 
ous and  interesting.  The  isobars  about  a  cy- 
clonic center  are  usually  nearly  circular,  but 
they  may  take  on  any  form  as  an  exception, 
and  Fig.  36  represents  an  occasional  one.  It 
has  an  extension  southward,  making  a  sort  of 
trough.  Drawing  through  it  the  line  A  B  and 
passing  it  through  the  center  (7,  then  calling 
this  line  the  critical  axis  of  the  cyclone,  we 
may  say  :  Tornadoes,  when  they  form,  are  most 

156 


TORNADOES  OR  INTENSE  LOCAL  WHIRLS.    157 


likely  to  be  made  near  the  critical  axis  of  a 
cyclone,  and  especially  near  its  southern  end. 

To  understand  better  the  reason  of  this,  let 
us  sketch  in  the  winds  for  such  a  cyclone. 
They  appear  as  in  the 
diagram  of  winds,  and 
it  appears  that  because 
of  the  stretching  out 
of  the  isobars  to  the 


FIG.  36. — Low  with  extension 
southward.  A  trouble 
breeder.  A  C  B  is  the  criti- 
cal line  and  C  the  center. 


FIG.  37.— The  winds  of  the  trouble 
breeder.  A  C  is  the  critical 
axis. 


southward  a  remarkable  condition  of  things 
exists  along  the  critical  axis  south  of  the  cen- 
ter. Here  the  southern  air  is  drawn  up  in 
nearly  straight  lines  toward  the  center,  while 
the  northwesterly  air  is  drawn  in  to  the  cy- 


158  ABOUT  THE  WEATHER. 

clone  in  such  a  way  as  to  meet  the  southerly 
winds  at  a  right  angle,  or  nearly  so,  and  this 
will  be  along,  or  near,  the  critical  axis  A  C. 

A  great  deal  of  disturbance  will  be  caused 
all  along  this  axis.  The  cold,  dry,  northwest- 
erly air  will  come  in  direct  contact  with  the 
warm,  moist,  southerly  air,  and  either  shove 
it  aside,  mix  up  with  it,  shove  under  it,  or  pass 
above  it.  In  any  case,  along  this  line  and  for 
a  region  on  each  side  of  it,  particularly  toward 
the  east,  there  wrill  be  many  local  disturbances 
of  the  weather,  among  which  may  be  thunder- 
storms, hailstorms,  and  tornadoes. 

When  the  disturbance  is  intense  a  tornado 
may  be  formed,  and  this  is  most  likely  to  occur- 
in  the  warmer  part  of  the  day,  when  the  sun 
also  aids.  To  the  onlooker  there  appears  a  great 
agitation  in  the  clouds,  especially  to  the  west. 
Then  a  whirling  motion  is  visible,  and  soon  a 
great  funnel-shaped  extension  is  let  down  to- 
ward the  earth.  It  is  seen  to  be  made  of  cloud 
in  violent  whirling  motion,  and  is  very  similar 
to  the  funnels  extended  downward  when  water- 
spouts are  formed,  as  described  by  sailors.  The 
funnel  is  not  steady,  but  swings  back  and  forth, 
something  like  the  trunk  of  an  elephant.  At 
first  it  does  not  reach  the  ground,  and  in  some 
cases  it  never  does,  being  withdrawn  gradu- 


TORNADOES  OR  INTENSE  LOCAL  WHIRLS.     159 

ally  before  it  attains  such  a  length  as  to  touch 
the  earth.  In  these  cases  there  are  no  destruc- 
tive winds,  but  observers  report  hearing  a  roar- 
ing sound.  The  facts  that  the  tornado  funnel 
is  gradually  extended  downward  from  the  air, 
and  that  tornadoes  may  exist  in  the  air  and 


FIG.  38.— Waterspouts. 

never  reach  the  earth,  indicate  that  their  home 
is  in  the  cloud  layer. 

If  the  funnel  continues  to  extend  down- 
ward, as  is  usually  the  case,  it  passes  along, 
swinging  from  side  to  side  and  making  occa- 
sional leaps  from  the  ground.  Me* 

Of 


.c*. 


160  ABOUT  THE  WEATHER. 

wherever  it  touches  it  leaves  death  and  destruc- 
tion behind  it.  It  takes  it  only  a  few  sec- 
onds to  pass  any  point,  but  after  it  has  passed 
the  place  is  hardly  recognizable.  One  gentle- 
man relates  that  he  was  sitting  in  his  house 
at  Viroqua,  Wis.,  and  his  horse  was  secured 
in  its  stable  some  little  distance  away.  A  tor- 
nado came  on  them  fairly  unawares,  and  a  few 
moments  afterward  he  came  to  consciousness 
lying  in  his  cellar,  his  house  gone,  his  horse's 
head  lying  across  him,  and  both  pinned  down 
by  timbers  and  fragments  of  buildings  from 
some  distance  around. 

Fig.  39  is  an  actual  photograph  of  a  tor- 
nado. It  is  the  one  that  visited  Lake  Gervais, 
Minnesota,  on  July  13,  1880.  The  photograph 
was  taken  at  a  distance  of  about  six  miles. 
The  funnel  can  be  seen  through  the  rain  that 
was  falling  between  it  and  the  photographer. 
This  tornado  was  a  severe  one  and  was  quite 
destructive.  Photographs  of  tornadoes  have 
several  times  been  made.  This  appears  to  be 
the  best  and  most  typical,  and  apparently  has 
been  little  touched  up  by  the  photographer. 

The  storm  sweeps  on  in  a  general  northeast- 
erly path,  and  lasts  but  an  hour  or  two.  It  is 
often  accompanied  by  very  remarkable  elec- 
tric phenomena,  the  air  being  heavily  charged 


TORNADOES  OR  INTENSE  LOCAL  WHIRLS.     163 

articles  have  sometimes  been  abstracted  by  the 
tornado  and  carried  far  away.  This  is  well 
illustrated  by  a  story  told  of  a  Tennessee  cabin 
over  which  a  light  tornado  passed  one  day. 
After  it  had  passed  by,  the  woman  of  the  little 
household  noticed  a  bright-colored  ribbon  hang- 
ing down  from  the  fireplace.  It  was  of  the 
color  of  the  ribbons  on  her  much-prized  bonnet, 
and  she  proceeded  at  once  to  investigate.  She 
found  it  was  indeed  her  bonnet  caught  on 
some  projections  of  the  mortar  in  the  flue  of 
the  fireplace.  The  bandbox  in  which  the  bon- 
net was  kept  was  found  open.  It  appears  that 
in  this  case  the  suction  action  of  the  storm  was 
enough  to  open  the  closed  bandbox  to  let  out 
a  gush  of  denser  air  that  carried  the  bonnet 
with  it  until  the  latter  was  caught  in  the  chim- 
ney. In  another  case  a  soldier's  discharge 
paper  is  said  to  have  gone  the  same  way. 

Now,  to  maintain  a  vacuum  that  will  ex- 
ercise so  great  a  suction  power  the  whirling 
must  be  indeed  intense,  and  that  it  is  so  is 
plainly  seen  to  be  from  its  effects.  It  plucks 
the  feathers  from  fowls,  drives  laths  through 
small  trees,  and  wrecks  or  twists  the  strongest 
structures  around.  In  some  cases  the  work  it 
has  done  enables  us  to  calculate  the  velocity  of 
the  wind  which  did  it,  and  this  has  been  found 


164  ABOUT  THE  WEATHER. 

to  amount  to  two  hundred  miles  an  hour. 
That  means  a  pressure  of  two  hundred  pounds 
on  each  square  foot  of  the  sides  of  buildings. 

Tornadoes  may  occur  almost  anywhere,  but 
in  the  United  States  they  are  most  common  in 
the  Mississippi  Valley  east  of  the  great  plains. 
They  are  fortunately  not  common,  for  they 
are  very  destructive.  The  area  over  which 
they  work  an  injury  is  small,  being  a  strip 
of  territory  rarely  aggregating  more  than  a 
square  mile  of  surface.  There  is  on  record 
an  average  of  fifty  of  them  a  year,  a  score  of 
which  have  done  injury  of  a  serious  character 
to  the  country  over  which  they  have  passed. 
This  would  mean  about  twenty  square  miles 
affected  each  year,  but  the  region  in  which 
they  are  likely  to  occur  is  a  million  and  a 
quarter  square  miles  in  extent.  The  prospect 
that  one  may  pass  this  year,  or  the  next,  over 
the  particular  square  mile  in  which  the  reader 

is  at  this  moment  is  therefore    '      ' — ,  or  one 

chance  in  625,000.  This  chance  is  not  worth 
worrying  about. 

Even  if  a  tornado  chanced  to  pass  over  a 
strip  in  which  the  reader  might  be,  it  would  be 
far  from  certain  death  to  him.  Indeed,  con- 
sidering the  amazing  violence  of  these  storms, 


TORNADOES  OR  INTENSE   LOCAL  WHIRLS.     165 

it  is  remarkable  that  the  deaths  from  them  are 
not  more  numerous.  It  is  only  when  they  pass 
through  populous  cities — as  Louisville  and  St. 
Louis — that  the  casualties  from  them  are  very 
numerous.  The  timid  who  live  outside  the 
tornado  area  worry  to  no  purpose.  Those  who 
live  in  the  region  affected  may  calm  themselves 
by  the  reflection  that,  taken  altogether,  there 
is  not  one  chance  in  a  million,  though  they  lived 
to  be  centenarians,  that  they  will  be  injured  by 
a  tornado. 


CHAPTER  XXL 

8TOEMS    OF   ICE,    SLEET,    BALL     SNOW,    AKD     HAIL. 

THE  storms  of  by  far  the  most  importance 
in  the  ice  series  of  local  storms  are  the  hail- 
storms. 

The  proper  ice  storm  is  that  which  covers 
the  ground,  roofs,  and  the  branches  of  trees 
with  a  thin  layer  of  ice  that  make  them  glit- 
ter in  the  sun,  giving  a  beauty  to  the  leafless 
trees  which  seems  quite  foreign  to  them.  The 
cold  that  here  changes  the  water  into  ice  is  in 
the  objects  on  which  the  rain  falls.  After  a 
long  winter  cold,  when  everything  is  full  of 
frost,  a  cyclone  comes  on  with  warmer  weather 
from  the  south  and  lets  fall  a  gentle  rain  on 
the  yet  ice-cold  objects  on  the  surface.  As 
soon  as  the  rain  touches  these  it  is  chilled,  and 
before  it  can  run  off  it  is  changed  to  solid  ice. 
If  the  objects  are  very  cold  and  the  rain  con- 
tinues some  time,  the  branches  and  telegraph 
wires  become  so  loaded  with  ice  as  to  be 
brought  down  by  their  own  weight.  This  is 

166 


OF    THE 

UNIVERSITY 


168  ABOUT  THE  WEATHER. 

an  unusual  atorm ;  rarely  more  than  one  a  year 
occurs,  and  sometimes  several  years  together 
pass  with  none  at  all. 

The  next  step  in  the  series  is  sleet.  It  con- 
sists of  snow  loaded  with  liquid  water.  The 
snow  crystals  are  doubtless  formed  in  a  cold, 
higher  layer  of  air.  In  descending  they  pass 
through  a  very  moist,  warm  layer,  and  the  wa- 
ter is  abundantly  condensed  on  their  surface. 
It  may  be  also  that  the  snow  is  in  part  melted. 
Sleet  is  common  enough,  occurring  usually  in 
the  spring  and  autumn. 

The  next  step  to  this  is  the  snow  proper. 
This  is  formed  in  the  clouds  and  descends 
slowly  with  little  whirling  motions.  The  for- 
mation must  be  in  gentle  or  calm  weather  when 
the  flakes  are  large,  and  in  any  case  the  motion 
of  the  air  at  the  place  of  formation  must  be 
slight.  Otherwise  the  flakes  would  not  be 
regular,  and  would  be  more  or  less  broken  and 
compacted  by  jostling  together. 

There  may  be  additions  to  the  flakes  as 
they  slowly  descend  through  the  air  below  the 
cloud  layer.  This  is,  in  all  probability,  often 
the  case  with  rain.  As  has  been  mentioned, 
the  opposite  condition  with  regard  to  rain  may 
often  be  seen  in  dry  climates ;  that  is,  rain  will 
form  in  the  clouds  and  be  seen  to  descend,  but 


ICE,  SLEET,   BALL  SNOW,  AND  HAIL.        169 

will  all  disappear  before  it  reaches  the  ground. 
It  is  evaporated  again  in  passing  through  the 
dry  air  below. 

The  next  grade  is  that  curious  fall  of  spring 
and  autumn  called  ball  snow.  The  elastic  par- 
ticles which  come  rattling  to  the  ground,  where 
they  dance  about  for  some  time  before  they 
come  to  rest,  are  of  the  size  of  medium  shot, 
and  are  white  like  snow,  though  they  are  so 
compact  that  they  do  not  break  in  striking  the 
sidewalk.  They  seem  to  be  snowflakes  which 
have  been  formed  when  there  was  intense  mo- 
tion, so  that  they  were  jostled  together  until 
they  took  on  a  rounded  form.  They  are  not 
frozen  raindrops,  for  in  that  case  they  would  be 
transparent.  The  clouds  from  which  they  fall 
show  no  signs  of  unusual  activity,  so  we  can 
only  conclude  that  the  whirls  which  gave  them 
their  form  were  above  the  clouds. 

And  here  we  are  introduced  to  the  idea 
that  there  are  whirls  among  the  clouds. 
There  are  not  infrequently  two,  and  sometimes 
more  than  two  layers  of  clouds,  the  one  above 
the  other.  We  have  found  that  the  tornado  is 
formed  in  the  lower  cloud  layer  from  which  it 
bores  a  way  down  toward  the  earth.  We  have 
also  noted  that  the  cloud  layer  is  one  of  great 
activity.  It  may  be  added  that  the  upper  sur- 


1YO  ABOUT  THE  WEATHER. 

face  of  a  cloud  must  act  toward  the  air  above 
it  much  as  the  surface  of  the  earth  acts  toward 
the  air  just  above  it.  It  is  therefore  probable 
that  between  two  cloud  layers  there  may  be 
whirls  as  between  the  earth  and  the  first  cloud 
layer.  Indeed,  in  one  case  at  least,  Wise,  the 
balloonist,  found  a  whirl  between  clouds,  and 
was  involved  in  it  to  his  own  great  danger. 
Adopting  the  idea  of  whirls  between  clouds — 
extremely  probable  in  itself,  though  they  are 
rarely  seen — the  explanation  of  the  mysterious 
hailstorms  becomes  much  easier. 

Hailstorms  are  hot-w^eather  local  storms 
characterized  by  the  fall  of  hail,  and  usually 
by  sharp  lightning  and  thunder.  They  are 
most  common  in  the  daytime  and  in  the  hot 
season  of  the  year.  They  rarely  occur  at  night. 
They  are  most  probable  when  the  day  is  hot 
and  dry,  but  the  night  gives  an  abundant  dew. 
The  cloud  forms  are  first  cirrus ;  then  this  sinks 
to  cirro-stratus,  and  this  still  farther  to  a  dark- 
gray  storm  cloud  out  of  which  the  hail  falls. 
The  hail  cloud  shows  a  strong,  heaving,  boiling 
motion,  and  from  its  bottom  often  hang  ragged 
fringes.  It  is  a  cloud  in  intense  activity,  but 
the  cause  of  the  motion  is  hidden  from  us.  It 
is  probably  a  strong  whirl  which  remains  above 
the  cloud. 


ICE,   SLEET,   BALL  SNOW,   AND  HAIL. 

The  approaching  storm  makes  a  curious 
crackling,  rushing  noise,  due  to  the  stones  strik- 
ing on  each  other.  The  stones  are  of  various 
forms.  The  commonest  are  flat  and  shaped 
like  a  lens.  Others  are  spherical,  sometimes 
smooth,  sometimes  knobby.  Still  others  have 
some  of  their  sides  flat  and  angular. 

A  common  size  for  a  hailstone  is  that  of  the 
pea,  less  often  that  of  a  large  bean,  sometimes 
that  of  a  hen's  egg.  Still  larger  are  sometimes 
recorded  on  good  authority ;  and  in  Kansas,  on 
August  15,  1883,  one  is  said  to  have  fallen 
which  weighed  eighty  pounds. 

The  total  amount  that  falls  from  a  hail 
storm  has  been  measured  and  estimated  several 
times.  In  Switzerland  in  1881  there  was  a 
hailstorm  of  only  a  few  minutes'  duration 
which  let  fall  hail  to  the  weight  of  a  hundred 
tons.  In  1788  a  storm  passed  through  France 
into  the  Netherlands,  from  which  descended 
on  the  earth  hailstones  to  a  weight,  estimat- 
ed by  a  recognized  authority,  as  aggregating 
four  hundred  thousand  tons.  That  is  a  larger 
amount  of  ice  than  there  is  in  some  glaciers. 

Hailstorms  occur  all  over  the  earth,  but  are 
not  so  common  at  high  elevations  and  in  high 
as  in  low  latitudes.  They  are  very  local  in 
character,  and  show  a  strong  inclination  to 

13 


172  ABOUT  THE  WEATHER. 

avoid  forests  and  mountains  and  to  travel 
along  valleys.  They  also  show  a  tendency  to 
come  again  to  a  place  visited  before ;  and  of 
two  places  not  far  apart,  one  may  be  frequently 
visited  and  the  other  not  at  all. 

The  destructive  effects  of  hail  are  great 
on  buildings — windows  especially  suffer — on 
growing  crops  and  vineyards,  and  on  small  ani- 
mals. The  destruction  is  so  great  that  com- 
panies insuring  against  hail  are  not  uncommon, 
particularly  in  the  Old  World.  In  this  coun- 
try such  companies  also  generally  insure  against 
injury  by  tornadoes.  There  are  also  many 
who  believe  that  hailstorms  may  be  prevented 
by  such  simple  means  as  planting  tall  poles  or 
firing  cannon. 

The  explanation  of  the  formation  of  hail 
has  already  been  suggested.  It  should  be 
added  that  when  hailstones  are  cut  open  they 
are  often  found  to  be  in  layers,  and  sometimes 
the  nucleus  is  a  little  sphere  of  ball  snow.  The 
form  of  most  hailstones  is  that  which  would  be 
given  them  if  they  were  set  spinning  in  the  air ; 
the  spinning  might  be  caused  by  a  strong 
whirl  like  a  tornado,  and  this  would  also  ac- 
count for  their  being  suspended  in  the  air  until 
they  had  grown  to  so  large  a  size.  We  can 
think  of  nothing  that  would  keep  them  in  the 


ICE,   SLEET,   BALL  SNOW,   AND  HAIL.         173 

air  until  they  weighed  from  an  ounce  to  many 
pounds,  except  the  very  strong  rising  winds  of 
a  whirl.  Moreover,  the  layers  into  which  they 
can  be  divided  would  indicate  that  they  had 
passed  through  the  whirl  several  times.  When 
driven  up  once  and  thrown  out  above  they 
must  have  been  caught  again  in  the  whirl,  and 
this  must  have  been  repeated  as  many  times 
as  they  have  layers.  At  last  they  would  be 
thrown  out  in  such  a  way  as  to  escape  the 
whirl  and  reach  the  earth. 


CHAPTER  XXII. 

THUNDERSTORMS    AND    CLOUD-BURSTS. 

THE  local  storms  classed  under  the  head  of 
thunderstorms  have  a  common  feature  in  the 
strong  electric  condition  shown  by  all  of  them. 
They  are  usually  rather  gentle,  for  when  in- 
tense they  -pass  into  storms  such  as  the  torna- 
does and  hailstorms  already  described,  or  into 
a  kind  of  storm  marked  by  especially  heavy 
local  rainfall  and  called  cloud-burst.  Thunder- 
storms otherwise  differ  very  much  among  them- 
selves, and  probably  include  a  large  number  of 
different  sorts  of  local  storms. 

For  instance,  they  are  found  under  three 
different  conditions.  The  first  kind  are  found 
along  the  critical  line  of  a  cyclone  ;  it  occurs 
in  the  same  weather  as  the  tornado,  and  may 
be  quite  intense.  Indeed,  in  this  class  there 
is  every  grade  of  intensity,  from  the  very 
gentle  shower  with  some  lightning,  to  well- 
marked  whirls  of  such  violence  that  they  might 
be  called  tornadoes. 

174 


THUNDERSTORMS  AND  CLOUD-BURSTS.       175 

The  second  occur  in  troops  or  herds  over 
regions  sometimes  as  large  as  a  State  or  two 
States,  sometimes  covering  only  a  quarter  of 
a  State,  or  a  less  area.  These  regions  may  be 
in  the  southeast  quarter  of  a  cyclone  or  have 
no  visible  connection  with  general  storms ; 
they  are  most  common  in  summer  and  in  the 
tropics,  and  the  region  over  which  they  are 
likely  to  crop  out  is  apt  to  be  one  that  has  great 
warmth,  little  wind,  and  much  moisture  in  the 
air.  Here  they  begin  to  develop  in  the  later 
morning  hours,  and  travel  eastward  during  the 
day,  disappearing  at  night.  They  are  usually 
many  miles  apart,  and  bring  the  light  showers 
of  haying  and  harvest  time  so  common  over  the 
Central  States.  After  a  thunderstorm  of  this 
sort  has  passed,  it  appears  to  exhaust  the  ca- 
pacity of  the  air  for  such  storms.  It  is  not  apt 
to  repeat  itself  for  several  days. 

The  third  sort  are  solitary  and  more  or  less 
dependent  on  the  features  of  the  surface.  They 
are  likely  to  start  up  in  valleys  or  at  the  base 
of  high  hills  or  mountains,  and  do  not  travel 
far.  The  weather  in  which  they  occur  is  much 
like  that  of  the  preceding. 

All  three  kinds  may  have  sharp  lightning 
and  thunder,  and  any  one  may  become  intense, 
though  this  is  much  more  likely  with  the  first 


176  ABOUT  THE   WEATHER. 

than  with  the  other  two  sorts.  The  third  is 
the  commonest  in  the  tropics,  where  it  shows 
a  decided  choice  for  certain  localities.  During 
favorable  weather  there,  one  is  likely  to  form 
daily  at  the  base  of  some  favorite  mountain. 
It  will  begin  to  form  its  cloud  cap  about  noon. 
By  four  in  the  afternoon  it  will  have  developed 
a  great  black  cloud  in  active  movement,  light- 
nings will  begin  to  flash,  the  thunders  to  roll, 
and  the  rain  to  come  down  ;  then  it  will  move 
nearer  the  mountain,  the  rains  will  increase,  and 
the  cloud  shut  out  the  declining  sun.  As  it 
exhausts  its  rain  it  will  move  away  and  soon 
will  begin  to  disappear.  By  ten  o'clock  at 
night  it  will  probably  be  all  gone,  and  the 
stars  shining  brightly  without  a  cloud  in 
the  sky. 

The  weather  in  which  thunderstorms  occur 
is  usually  warm,  the  season  the  hot  time  of 
the  year,  and  the  hour  the  warm  hours  of  the 
day;  but  there  are  exceptions,  thunderstorms 
sometimes  occuring  even  at  the  coldest  time 
in  the  night.  Winter  thunderstorms  are  also 
known.  Both  these  latter  are  generally  stronger 
and  more  destructive  than  the  others,  and  the 
winter  storms  are  usually  distinct  whirls  ;  at 
least  this  is  the  case  along  the  Norwegian  coast, 
where  they  have  been  studied  by  Mohn. 


THUNDERSTORMS  AND  CLOUD-BURSTS. 

Thunderstorms  are  usually  on  the  surface, 
or  between  that  and  the  lower  layer,  of  clouds. 
In  this  case  they  bring  a  decided  change  of 
temperature  with  them.  The  air  is  cooler  and 
the  wind  changes.  A  few  seem  to  be  in  the 
upper  air,  and  some  even  may  permit  a  few 
hailstones  to  escape  above.  These  are  transi- 
tion forms  toward  well-developed  hailstorms. 

In  the  case  of  the  cloud-burst  there  is  little 
on  the  surface  of  the  earth  to  show  that  im- 
mense quantities  of  water  are  confined  above. 
The  clouds  are  dark  gray  or  black,  and  are  in 
active  turmoil.  Lightning  strikes  through  them 
from  time  to  time,  but  there  is  no  noteworthy 
change  at  the  surface  of  the  earth  until  sud- 
denly something  seems  to  give  way  above,  and 
a  deluge  of  rain  descends.  These  sudden  down- 
pours occur  in  dry  regions,  and  though  the 
cloud  often  bursts  in  the  free  air,  it  is  more 
likely  to  do  so  if  it  drifts  against  a  mountain. 

Thunderstorms  differ  in  being  stationary 
or  progressive,  and  there  are  all  stages  between 
those  which  do  not  move  at  all  and  those  which 
travel  eastward  at  the  rate  of  twenty  or  thirty 
miles  an  hour.  There  is  one  common  form 
which,  as  it  moves  forward,  spreads  out  like  a 
fan,  and  as  it  does  so  divides  up  into  many 
thunderstorms.  The  map  of  such  a  rank  of 


178  ABOUT  THE  WEATHER. 

storms  is  like  the  diagram.  The  point  of  be- 
ginning is  about  C.  As  it  starts  eastward  it 
spreads  out  along  a  curved  line  which  divides 
up  into  several  storms.  More  and  more  active 
centers  with  electric  phenomena  develop  as  it 
goes  on  eastward.  For  successive  hours  these 
are  found  along  the  curved  lines  marked  1, 
2,  3,  and  so  on.  Finally,  after  a  few  hours 


c  5 


6 
FIG.  41. — Ranks  of  thunderstorms  gradually  deploying. 

they  weaken  and  disappear.  This  form  of 
ranked  thunderstorms  has  been  called  a  de- 
recho. 

The  nature  of  the  motion  in  thunderstorms 
is  probably  various.  Some  are  certainly  as- 
cending whirls.  A  few  have  been  found  to  be 
small  descending  currents  of  air.  In  many 
cases  they  occur,  apparently,  along  a  small  wave 
of  pressure  in  the  air.  This  wave  usually  has 


THUNDERSTORMS  AND  CLOUD-BURSTS.       179 

its  hollow  at  about  the  moment  the  thunder- 
storm breaks,  and  its  crest  just  after.  Prob- 
ably in  the  derecho  the  curved  lines  1,  2,  3 
mark  the  successive  positions  of  this  crest. 
The  change  in  pressure  is  small,  and  requires 
close  observation  to  detect.  Just  in  front  of 
such  a  crest  must  be  a  considerable  up-and- 
down  change  in  the  air.  It  may  be  like  the 
critical  axis  of  a  cyclone,  and  the  phenomenon 
may  consist  of  small,  temporary  highs,  lows, 
or  horizontal  walls. 

Especial  study  of  thunderstorms  has  been 
made  in  the  last  few  years,  for  the  reason  that 
they  are  likely  to  do  injury  to  agriculture  and 
commerce,  because  of  their  sudden  and  unex- 
pected appearance.  They  may  catch  a  farmer 
in  the  midst  of  his  haying  and  seriously  injure 
his  crop,  or  take  a  sailing  vessel  unawares  and 
capsize  it.  The  attempts  at  predicting  their 
appearance  at  any  given  time  or  place  have 
been  barely  successful,  but  the  warnings  less 
satisfactory.  The  storms  are  short-lived,  and 
the  people  to  be  warned  are  at  some  distance 
from  a  telegraph  or  telephone  station.  The 
progress  of  the  storms  can  sometimes  be  safely 
forecasted  for  several  hours,  but  this  is  not 
time  enough  to  reach  and  warn  the  persons 
whose  interests  are  in  danger. 


CHAPTER  XXIII. 

LIGHTNING    AND    THUNDEE. 

THERE  is  as  yet  no  good  reason  for  think- 
ing that  electricity  is  one  of  the  great  causes  of 
the  weather  and  its  changes.  On  the  other 
hand,  it  is  probably  only  an  effect  having  very 
little  to  do  with  the  weather,  except  to  add 
to  the  beauty  and  terrors  of  its  storms,  espe- 
cially when  these  are  intense.  It  has  one  sec- 
ondary effect  which  is  interesting,  and  that  is 
that  after  a  sharp  stroke  of  lightning  the 
rain  and  hail  fall  more  freely  than  before.  It 
may  be  that  electricity  in  some  way  is  instru- 
mental in  holding  up  the  drops  of  rain  and 
the  hailstones,  or  rather  aids  the  other  forces 
in  holding  them  up,  and  that  when  it  is  dis- 
charged they  fall ;  but  no  one  yet  understands 
how  this  action  could  be  exerted.  As  an  effect 
of  storms — sometimes  a  very  important  one,  and 
always  one  which  strongly  attracts  the  atten- 
tion, and  sometimes  causes  serious  loss,  and 
even  death  itself — the  subject  deserves  discus- 
sion. 

180 


LIGHTNING   AND  THUNDER.  181 

Now,  the  earth  and  the  air  are  contrasted 
as  to  their  electric  condition.  The  air  is  posi- 
tive and  the  earth  negative.  This  produces  an 
electric  strain  or  tension  between  them.  This 
strain  they  are  always  striving  to  neutralize  by 
a  discharge  from  one  to  the  other. 

Moreover,  friction  makes  electricity  or  in- 
creases the  strain  between  the  positive  and 
negative.  By  rubbing  together  the  folds  of 
the  soft,  light  rubber  cloth  used  by  dentists 
this  strain  can  be  increased  until  long,  sharp 
sparks  can  be  drawn  from  it  by  pointing  the 
finger  at  it,  thus  reducing  the  strain.  The 
same  thing  can  be  done  by  scraping  the  feet 
along  the  carpet  in  a  dry,  well-heated  room  in 
winter.  The  person  then  becomes  so  charged 
with  this  strain  that  he  can  bring  out  a  spark 
from  himself  by  pointing  his  finger  at  some 
one  else,  or  at  a  piece  of  metal.  He  can  even 
light  the  gas  by  the  spark  when  the  conditions 
are  very  favorable.  In  some  cases,  too — as 
when  the  air  is  very  dry  and  warm — the  strok- 
ing of  a  cat  brings  out  a  series  of  sparks. 

In  the  air  there  is  constant  rubbing  or 
friction,  and  this  tends  to  sharpen  the  strain. 
Thus  the  sand  becomes  charged  when  blown 
by  a  high  wind  over  a  desert,  and  it  is  doubt- 
less in  a  similar  way  the  clouds  become  highly 


182  ABOUT  THE  WEATHER, 

charged.  The  result  of  all  motions  of  the  air 
is  to  make  the  stress  stronger  between  air  and 
earth,  and  to  increase  the  tendency  to  relieve 
it  by  some  kind  of  a  discharge. 

The  discharge  is  likely  to  occur  at  all  points 
reaching  out  from  the  earth.  Thus,  on  a  high, 
isolated  mountain,  the  discharge  can  be  found 
at  almost  any  time.  When  the  strain  is  high— 
as  during  a  storm — the  discharge  may  occur 
over  a  tree,  and  through  it,  or  through  a  horse, 
or  man,  or  house,  or  anything  which  is  con- 
nected with  the  earth  and  stands  up  above  it. 
The  strain  is  particularly  severe  in  snowstorms, 
in  some  of  which  the  cloud  seems  to  actually 
come  dowrn  to  the  earth. 

The  discharges  are  gradual  or  abrupt. 
Among  the  gradual  discharges  is  the  one  that 
is  heard  but  not  seen.  It  is  experienced  on 
mountain  tops  especially,  and  the  one  who  is 
there  can  hear  the  crackling  buzzing  from  his 
hair  or  his  alpenstock.  It  often  sounds  like 
the  buzzing  of  a  bumblebee,  and  those  who  do 
not  know  about  it  try  to  find  the  bee  and 
drive  it  away.  They  may  be  tormented  by 
the  idea  that  it  is  in  some  one's  hat  and  fear 
that  it  will  sting,  but  they  hunt  for  it  in 
vain. 

Another    slow    discharge    is    visible,   but 


LIGHTNING  AND  THUNDER.  183 

makes  little  or  no  noise.  It  appears  like  a 
little  lambent  flame  on  the  head,  on  the  vizor 
of  the  cap,  on  the  shoulders,  the  cane,  on  the 
angles  of  stones — wherever  there  is  a  projecting 
point.  There  is  no  heat  and  no  danger  in  the 
flame,  and  no  danger  generally  in  these  slow, 
gentle  exchanges  of  electricity  between  air  and 
ground.  Such  lambent  flames  are  occasion- 
ally seen  in  snowstorms  even  at  the  surface 
of  the  earth,  but  they  are  most  common  on 
mountain  tops.  The  St.  Elmo's  fire  that  ap- 
pears as  flames  on  the  masts  of  ships  in  some 
storms  is  an  instance  of  this  kind  of  electric 
discharge. 

A  very  curious  but  rare  form  of  discharge 
is  what  is  called  ball  lightning.  In  this  case 
a  white  ball,  as  if  of  cotton  waste,  descends 
quietly  in  the  air  and  rolls  along  the  ground. 
One  once  descended  upon  a  load  of  lumber, 
rolled  along  the  boards,  dropped  off  at  the  end 
of  the  wagon,  and  disappeared ;  another  came 
in  the  open  door  of  the  cabin  of  a  French 
peasant,  rolled  across  the  floor,  and  disappeared 
up  the  chimney  of  the  fireplace.  Ball  light- 
ning is  not  often  seen,  and  any  explanation  of 
its  form  or  causes  is  yet  unknown. 

An  abrupt  discharge  of  electricity  during  a 
thunderstorm  is  the  lightning ;  the  tension  be- 


184  ABOUT  THE   WEATHER. 

tween  cloud  and  earth  goes  on  increasing  until 
it  becomes  strong  enough  to  break  its  way 
through  the  air  between.  The  discharge  seems 
to  be  one,  but  photographs  show  that  there  are 


FIG.  42. — From  a  photograph. 


many  plays  of  the  electric  fluid  back  and  forth 
between  the  air  and  earth,  all  in  extremely  rapid 
succession.  The  discharge  is  an  electric  spark 
like  that  drawn  from  an  electric  machine,  which 


LIGHTNING  AND  THUNDER.  185 

latter  we  can  make  only  a  few  feet  in  length. 
Nature  makes  them  thousands  of  feet  long. 

The  discharge  breaks  and  splits  trees,  or 
even  resolves  them  into  splinters  like  kindling 
wood,  because  it  heats  them  intensely,  and  this 
suddenly  makes  high-pressure  steam  which  ex- 
plodes. It  tears  the  boards  from  houses  or  sets 
them  on  fire  for  the  same  reason.  Its  fatal  ef- 
fects on  life  seem  to  be  due  not  so  much  to  the 
burning,  and  not  at  all  to  explosion,  but  to 
the  shock.  Hence  it  happens  that  persons 
made  insensible  by  a  stroke  of  lightning  can 
often  be  brought  to  if  immediately  cared  for. 

Danger  from  lightning  is  almost  nothing 
provided  one  keeps  away  from  high  places  and 
from  under  trees  during  a  thunderstorm,  or 
has  his  house  properly  protected.  Houses  in 
cities  are  very  rarely  struck.  They  are  so  full 
of  iron  and  other  metal,  and  this  is  in  such 
complete  connection  with  the  earth  through 
the  water  and  gas  pipes  that  the  tension  above 
them  is  relieved  by  constant  and  silent  ex- 
change between  the  air  and  the  earth.  It  is 
the  house  or  barn  that  stands  alone  and  with- 
out high  trees  around  it  that  needs  to  be  pro- 
tected. 

The  principle  in  lightning  conductors  is 
that  they  must  connect  with  the  deeper  moist 


186  ABOUT  THE  WEATHER. 

earth  through  a  good  conductor  of  electricity 
those  parts  of  the  house  most  likely  to  be 
struck.  Flat  bands  of  copper  are  the  best  con- 
ductors. Metal  points  on  the  house  tend  to 
produce  a  silent  and  harmless  discharge  be- 
tween air  and  earth.  The  most  common  causes 
of  failure  in  lightning  rods  are  carelessness  and 
neglect.  The  rods  are  not  large  enough  to 
conduct  a  heavy  stroke,  or  they  are  not  properly 
connected  with  the  deeper  damp  soil,  or  they 
have  been  neglected  and  become  broken  or  im- 
perfect. A  poor  or  imperfect  rod  is  worse  than 
none. 

The  broad,  silent  flashes  of  light  between 
clouds  are  reflections  on  the  clouds  of  lightning 
so  distant  that  the  thunder  can  not  be  heard. 
The  thunder  is  the  sound  of  the  sudden  coming 
together  of  the  air,  violently  torn  apart  by  the 
heat  and  energy  of  the  lightning.  This  series 
of  sounds  is  echoed  and  reflected  from  distant 
objects,  thus  giving  the  roll  of  the  thunder. 
The  sound  of  the  thunder  comes  much  more 
slowly  than  the  light  of  the  lightning.  If  one 
will  count  the  number  of  seconds  between  the 
flash  and  the  flrst  hearing  of  the  thunder  and 
divide  by  five,  it  will  give  closely  enough  in 
miles  the  distance  at  which  the  flash  took  place. 


CHAPTEK  XXIY. 

THE   WEATHER   PROGRESS    THROUGH   THE   DAY 
AND    YEAR. 

THE  daily  change  in  sunshine,  alternating 
with  darkness,  causes  a  change  in  all  the  me- 
teorological elements,  and  this  is  enough  to 
control  the  occurrence  of  local  storms,  but  not 
enough  to  have  a  marked  effect  on  general 
storms  or  anticyclones.  The  change  is  there- 
fore by  far  most  appreciable  in  intermediate 
weather.  It  is  most  noteworthy  in  the  winds 
when  not  controlled  by  great  centers  of  pres- 
sure. In  all  cases  not  so  controlled  the  move- 
ment of  the  sun  causes  a  change  in  the  direction 
of  the  wind,  which  varies  with  the  character  of 
the  country  around  the  station. 

It  is  most  interesting  in  the  case  of  stations 
on  the  coast,  where  it  gives  rise  to  land  and  sea 
breezes.  In  the  daytime  the  land  becomes 
heated  until  it  is  warmer  than  the  water.  The 
heavier  air  of  the  ocean  then  presses  in  on  the 
lighter  air  over  the  land,  the  latter  rises,  and 

H  187 


188  ABOUT  THE   WEATHER. 

the  former  flows  in,  producing  the  sea  breeze. 
This  begins  along  in  the  day,  reaches  its  great- 
est strength  late  in  the  afternoon,  and  dies  out 
early  in  the  night.  The  sea  then  becomes 
warmer  than  the  land,  and  the  opposite  process 
takes  place,  making  the  land  breeze.  These  oc- 
cur only  when  the  land  is  free  from  snow  and 
is  not  so  chilled  by  the  cold  of  winter  that  the 
temperature  of  the  soil  may  not  be  notably  in- 
creased by  the  rays  of  the  sun. 

The  land  and  sea  breezes  belong  to  the 
warmer  parts  of  the  earth  and  to  the  warmer 
season  of  the  year.  They  occur  on  the  Ameri- 
can coast  to  New  England  at  least  on  the  north, 
over  the  coast  of  the  Gulf  of  Mexico,  where 
they  often  extend  far  inland,  and  over  the  Pa- 
cific coast  to  Washington  in  clear  weather. 
They  also  occur  to  a  less  degree  and  less  regu- 
larly about  such  large  bodies  of  water  as  the 
Great  Lakes. 

A  similar  daily  change  takes  place  among 
mountains  when  the  air  passes  up  the  valley 
during  the  hot  part  of  the  day,  and  down  dur- 
ing the  colder  part  of  the  night. 

The  meteorological  equator,  or  equator  for 
the  weather,  is  called  the  heat  equator.  It  is 
near  where  the  sun  is  vertical  at  noon  and  hence 
changes  with  the  year,  being  so  high  north  in 


PROGRESS  THROUGH  THE  DAY  AND  YEAR.  189 

midsummer  as  to  pass  just  south  of  the  penin- 
sula of  Florida,  and  so  far  south  in  midwinter 
as  to  cross  the  continent  of  South  America 
on  the  parallel  of  Rio  Janeiro.  The  ring  of 
stormy  weather  over  the  temperate  zone  moves 
back  and  forth  with  the  motions  of  the  heat 
equator.  It  has  fairly  passed  to  the  north  of 
the  United  States,  except  Alaska,  in  the  hot- 
test part  of  the  year,  so  that  there  we  have 
very  few  general  storms  in  that  season.  In  the 
coldest  season  it  passes  to  the  farthest  south, 
and  reaches  about  to  the  coast  of  the  Gulf  of 
Mexico.  The  result  is  that  in  the  southern  tier 
of  States  there  are  few  general  storms  except 
in  winter,  while  in  the  Northern  States  gen- 
eral storms  cross  the  country  from  autumn  to 
spring. 

Just  south  of  this  band  of  general  storms  is 
the  region  of  local  storms.  This,  like  the 
other,  also  moves  back  and  forth  through  the 
year,  with  the  result  that  in  the  southern  tier 
of  States  there  are  local  storms  in  the  spring, 
summer,  and  autumn,  while  in  the  northern  tier 
they  occur  only  in  the  hot  season.  In  both 
cases  the  States  lying  between  the  northern 
and  southern  tiers  have  an  intermediate  con- 
dition as  to  the  times  of  general  and  local 
storms. 


190  ABOUT  THE  WEATHER. 

Tornadoes  take  a  somewhat  different  course 
through  the  year,  because  the  American  au- 
tumn is  too  dry  to  sustain  them.  They  are 
likely  to  begin  their  season's  work  in  the  Gulf 
States  in  February  and  March,  and  to  come 
gradually  northward.  They  appear  in  the 
Middle  States  in  April,  May,  and  June,  and 
in  the  higher  Mississippi  Valley  and  the  States 
about  the  Great  Lakes  in  summer.  They  are 
not  common  in  the  autumn  and  very  infrequent 
in  December  and  January. 

There  are  certain  well-marked  rainy  seasons 
in  the  United  States.  In  the  winter  the  Pacific 
coast  has  a  definite  season  of  rain,  beginning  in 
the  late  autumn  and  ending  in  the  early  spring. 
Local  storms  during  the  rest  of  the  year  are 
rare  there,  and  lightning  is  very  uncommon. 
In  the  spring  and  early  summer  there  is  a  mod- 
erate rainy  season  east  of  the  Rocky  Mountains 
from  Colorado  northward  into  Canada  and 
northeastward  to  Lake  Superior.  It  generally 
ends  in  June.  In  Arizona  and  New  Mexico 
there  is  a  rainy  season  in  late  summer,  due 
almost  entirely  to  local  storms.  In  the  autumn 
a  rainy  season  comes  on  in  Florida,  especially 
on  the  Atlantic  coast.  Its  influence  extends 
northward  well  up  toward  Cape  Hatteras  and 
westward  for  a  short  distance  on  the  Gulf 


PROGRESS  THROUGH   THE   DAY  AND   YEAR.     191 

coast.  The  rest  of  the  United  States  is  driest 
in  the  late  summer  and  the  autumn. 

In  some  parts  of  the  world  there  is,  accord- 
ing to  the  season,  a  change  of  wind  of  a  char- 
acter like  that  of  the  daily  exchange  of  land 
and  sea  breezes  already  described.  In  the  sum- 
mer the  land  area,  especially  the  dry  interior, 
gets  so  heated  that  the  air  tends  to  rise  and 
the  sea  air  to  pour  in  to  take  its  place.  In  the 
winter  the  opposite  is  the  case.  This  is  called 
a  monsoon,  and  is  very  appreciable  in  summer 
in  favorable  weather  over  the  Mississippi  Val- 
ley, generally  to  the  west  of  that  river.  The 
Gulf  wind  then  passes  generally  over  Texas, 
and  under  favorable  circumstances  occasionally 
reaches  the  Canadian  border. 

There  are  a  few  special  periods  of  weather 
through  the  year  which  are  of  great  interest. 
Beginning  with  January,  the  coldest  days  of  the 
year  are  likely  to  occur  for  two  or  three  weeks 
from  the  middle  of  that  month.  The  aver- 
age coldest  day  of  the  year  is  about  January 
25th,  or  about  a  month  after  the  winter  solstice, 
when  the  sun  is  farthest  south.  This  delay  of 
a  month  is  due  to  the  slowness  with  which  the 
earth  and  air  lose  their  heat. 

February  2d  is  a  day  that  has,  and  has  had 
for  ages,  a  curious  degree  of  popular  interest 


192  ABOUT  THE   WEATHER. 

without  any  justification  in  fact  that  has  been 
shown  by  American  weather.  It  is  an  excel- 
lent illustration  of  how  pleasing  notions,  once 
formed,  will  persist  without  reason  for  many 
hundreds  of  years.  This  day  is  Candlemas 
Day,  called  in  the  United  States  Groundhog  or 
Woodchuck  Day.  Of  this  day  the  old  country 
people  in  Scotland  say : 

"  If  Candlemas  is  fair  and  clear, 
There'll  be  two  winters  in  the  year." 

In  America  the  tradition  is  that  on  this  day 
the  woodchuck  comes  out  of  his  winter  resting 
place,  and  if  he  sees  his  shadow  he  returns  for 
six  weeks.  Nearly  all  the  European  peoples 
have  somewhat  similar  associations  with  the 
day.  The  weather  idea  underlying  is  that  if 
clear  weather  has  come  on  by  the  2d  of  Feb- 
ruary a  new  period  of  winter  will  set  in  and 
spring  will  be  late.  There  is  no  reason,  so  far 
as  weather  statistics  show  us,  for  this  conclusion. 

About  the  middle  of  May  frosts  are  likely 
to  recur  both  in  Europe  and  in  America.  In 
central  Europe  the  recurrence  is  supposed  to 
take  place  on  the  llth,  12th,  and  13th  of  May, 
and  the  saints  for  these  days  are  called  the  ice 
saints,  because  they  bring  ice  out  of  season,  and 
vine  stealers,  because  the  frosts  of  this  date  are 


PROGRESS  THROUGH  THE  DAY  AND  YEAR.  193 

likely  to  injure  the  vines.  In  the  States  there 
is  also — at  least  in  the  North — some  probability 
of  frost  in  the  latter  part  of  June. 

The  hottest  day  in  the  year  falls  generally 
after  the  middle  of  July,  about  a  month  after 
the  summer  solstice.  The  sun  is  highest  at  the 
latter  date,  and  the  delay  of  a  month  is  due 
to  the  slowness  with  which  the  earth  and  air 
heat  up. 

In  the  latter  part  of  October  or  early  in 
November  there  are  often  several  days  of 
warmer  weather,  corresponding  in  untimeliness 
to  the  May  frosts.  They  are  called  Indian 
summer  in  the  States,  but  St.  Martin's  summer 
in  Canada,  after  the  saint  of  November  llth. 
These  days  in  the  States  are  usually  character- 
ized by  a  blue  haze  or  smoke  in  the  air,  which 
makes  them  very  attractive,  and  they  are  gener- 
ally calm.  The  smoke  is  sometimes  attributed 
to  the  burning  off  of  the  trash  of  clearings, 
which  is  likely  to  be  done  about  that  time, 
because  the  dry  weather  preceding  has  made 
it  ready  and  the  winter's  approach  makes 
further  delay  undesirable. 


CHAPTEK  XXY. 

LOCAL    INFLUENCES    ON    WEATHER. 

LOCAL  features,  such  as  mountains,  forests, 
lakes,  have  a  noteworthy  effect » on  the  weather, 
so  great  as  appreciably  to  add  to  or  subtract 
from  the  prosperity  and  comfort  of  those  who 
live  near  them.  The  coast  weather  is  always 
less  variable  than  the  weather  in  the  interior 
of  a  continent.  Continental  weather  has  sud- 
den and  severe  changes  of  temperature,  which 
are  very  trying  to  those  who  endure  them,  but 
which  tend  to  make  the  strong  stronger.  This 
is  the  case  to  an  especial  degree  in  the  middle 
of  the  continent  of  North  America,  because  no 
lofty  mountains  shut  off  from  it  the  cold  air 
which  at  times  sweeps  down  from  the  polar 
regions.  The  same  is  true  of  the  most  of  Siberia ; 
but  Mongolia  is  protected  from  the  north  by 
mountains,  as  is  also  the  valley  of  the  Amur. 
These  regions  are  in  the  latitude  of  the  northern 
United  States,  and  their  climate,  when  of  the 
same  degree  of  dry  ness,  is  somewhat  superior  to 

194 


LOCAL  INFLUENCES   ON   WEATHER.  195 

that  of  the  interior  of  the  States.  The  climate  of 
the  western  plains,  even  as  far  south  as  Texas,  is 
subject  to  these  severe  changes  of  temperature. 

On  the  other  hand,  the  coast  is  subject  to 
a  greater  amount  of  cloud  and  fog,  and  to  a 
moisture — which  though  comfortable  in  mod- 
erate weather  is  very  uncomfortable  when  the 
temperature  is  extreme ;  close  and  weakening 
when  it  is  very  hot ;  raw  and  searching  when 
it  is  very  cold.  So  the  balance  is  pretty  well 
preserved  in  the  United  States  between  the  in- 
terior and  the  coast. 

Fog  is  generally  confined  to  the  coast  and 
to  the  mountains.  It  is  most  abundant  and 
continuous  on  the  coast  of  the  extreme  North- 
west, where  it  may  occur  for  many  days  in 
succession,  and  it  sometimes  lasts  all  day.  It  is 
next  most  common  on  the  northern  Atlantic 
coast.  It  is  frequent  on  the  Great  Lakes  in 
summer,  and  especially  on  Lake  Superior.  Fog 
makes  depressing  weather,  not  lessened  by  the 
dismal,  oft-repeated  moans  of  the  warning  fog 
horns  near  the  harbors. 

One  of  the  features  of  what  may  be  called 
artificial  weather  is  the  frequency  of  fogs  near 
and  over  great  cities  on  the  coast.  The  fog 
grows  more  frequent  and  denser  and  continues 
longer  in  proportion  as  the  city  increases  in  size. 


196  ABOUT  THE   WEATHER. 

This  is  due  to  the  dust  and  smoke  produced, 
for  these  are  fog-compellers,  as  already  ex- 
plained. The  fogs  in  London  in  winter  are  so 
dense  as  to  practically  interrupt  traffic  while 
they  continue.  They  are  not  so  bad  in  New 
York,  but  are  already  at  times  a  serious  hin- 
drance to  commerce. 

An  effective  weather  control  is  a  range  of 
high  mountains,  especially  when  it  crosses  the 
usual  direction  of  the  wind.  This  is  the  case 
in  the  United  States  with  the  Rocky  Mountains 
and  the  ranges  along  the  Pacific  coast.  The 
effect  is  less  in  regions  subject  to  frequent  gen- 
eral storms,  as  in  the  extreme  Northwest,  but 
even  here  it  is  generally  appreciable. 

For  instance,  in  the  State  of  Washington 
the  Cascade  range  is  not  very  high.  The 
western  slope  is  covered  with  a  dense  growth 
of  magnificent  trees,  the  finest  forest  of  large 
trees  in  the  United  States  and  one  of  the  finest 
in  the  world.  The  forest  is  so  dense  that  it  is 
difficult  to  force  one's  way  through  it.  A  few 
miles  on  the  railway,  and  a  passage  perhaps 
through  a  short  tunnel,  brings  one  out  on  the 
eastern  slope  of  these  mountains,  and  he  seems 
to  have  passed  into  another  world.  There 
are  but  a  few  scattering,  small  trees  on  the 
mountain  side,  which  are  of  other  species  than 


LOCAL  INFLUENCES  ON  WEATHER.  197 

those  of  the  more  densely  wooded  slopes. 
Away  off  to  the  east  are  plains  on  which 
not  a  single  tree  is  to  be  seen,  except  where  it 
has  been  planted  by  settlers,  or  maintains  a 
precarious  existence  in  some  canon,  above  whose 
top  it  hardly  dares  to  peep.  The  rainfall  on 
the  western  slope  is  forty  to  sixty  inches  ;  on 
the  eastern  side  it  is  only  a  quarter  as  much. 
On  the  western  side  the  trees  protect  each  other 
from  the  wind,  but  on  the  eastern  the  light 
rainfall  does  not  permit  them  to  gain  sufficient 
vitality  for  this. 

The  wind,  carrying  a  load  of  moisture  from 
the  warm  Pacific,  strikes  on  the  western  slopes 
of  the  mountains  and  is  forced  upward  until 
it  is  chilled.  It  is  then  unable  to  sustain  its 
load  of  moisture,  and  deposits  it  abundantly 
in  the  form  of  rain'  or  snow  on  the  western 
side.  As  it  comes  down  on  the  eastern  side  it 
warms  again,  and,  having  lost  its  abundant 
humidity,  is  dry.  The  little  rain  that  falls  here 
is  due  to  the  general  storms,  that  bring  in 
some  air  from  the  north  which  has  not  crossed 
the  mountains.  Farther  south,  where  general 
storms  are  less  common,  as  in  Nevada,  the 
dry  ness  on  the  eastern  slope  is  extreme. 

As  the  storm  passes  east  in  the  higher  lati- 
tudes it  succeeds  in  storing  up  some  more 


198  ABOUT  THE  WEATHER. 

moisture,  and  this  it  deposits,  though  rather 
scantily,  on  the  next  range  of  mountains,  the 
Bitterroot  and  Cceur  d'Alene ;  and  here  is  an- 
other, but  less  abundant,  timber  growth,  and 
each  high  elevation  between  the  two  has  a  few 
trees.  It  strikes  the  mountains  again  in  the 
vicinity  of  Helena,  where  another  and  thinner 
forest  growth  exists,  and  it  finally  comes  out 
on  the  plains  fairly  devoid  of  moisture.  Thus 
the  western  slope  of  these  mountains  is  always 
more  moist  than  the  eastern,  the  plains  to  the 
east  of  the  mountains  are  dry,  and  this  dryness 
is  greater  the  farther  south  we  go. 

Such  is  not  the  case  with  the  Appalachian, 
Adirondack,  and  White,  and  Green  Mountains, 
partly  because  they  are  constantly  crossed  by 
general  storms,  partly  because  they  are  low, 
and  partly  because  the  moist  weather  from  the 
Atlantic  reaches  them. 

Another  effect  of  mountains,  in  this  case 
true  of  less  pretentious  elevations,  is  that  sec- 
tion called  the  warm  zone,  because  warmer  in 
winter  than  the  bands  higher  up  or  lower  down. 
This  is  especially  noticeable  on  the  Appala- 
chians, and  is  due  to  air  drainage. 

Cold  air  is,  as  has  often  been  said,  heavier 
than  warm  air,  consequently,  it  flows  down  in- 
clines like  water  and  seeks  the  lowest  levels. 


LOCAL  INFLUENCES   ON  WEATHER.  199 

In  cold,  quiet  weather  it  chills  the  lower  places 
and  leaves  the  warmer  air  above.  This  effect 
extends  up  to  a  limit,  where  it  is  balanced  by 
the  increased  bareness  and  exposure  which  per- 
mits a  greater  loss  of  heat  to  the  sky.  Hence 
between  this  higher,  more  exposed  zone  and  the 
lower  level  filled  with  cold  air  lies  a  band  of 
milder  temperatures. 

This  band  is  favorable  to  the  farmer,  and 
he  can  take  advantage  of  the  air  drainage  in 
other  ways.  For  instance,  in  southern  Michi- 
gan the  climate  is  almost  too  cold  for  the  finer 
kinds  of  peaches.  In  hollows  and  on  level  hill- 
tops the  trees  are  almost  invariably  injured  by 
winter  cold.  If,  however,  the  orchardist  will 
plant  them  on  a  slope,  so  that  the  cold  air  may 
drain  off,  he  will  be  able  to  raise  peaches  suc- 
cessfully. 

Another  and  very  remarkable  effect  of  moun- 
tains is  seen  in  the  Chinook  winds,  which  inter- 
rupt the  cold  of  winter  with  an  almost  spring- 
like mildness  on  the  plains  east  of  the  moun- 
tains from  Colorado  to  the  Peace  Kiver  in 
Athabasca,  The  Chinooks  are  westerly  winds 
which  bring  mild  temperatures,  and  are  so  dry 
that  they  evaporate  the  snow  without  melting 
it.  These  are  the  winds  which  descend  the 
mountains  and  become  warm  by  forcing  their 


200  ABOUT  THE  WEATHER. 

way  down  into  denser  air.  They  have  been 
made  dry  by  the  series  of  mountain  ranges  they 
have  crossed.  They  render  the  climate  of  the 
northern  plains  much  more  inhabitable  than 
they  would  otherwise  be,  and  in  the  United 
States  their  influence  reaches  eastward  to  Min- 
nesota. 

A  still  more  noteworthy  wind  of  this  sort 
occurs  in  the  Alps,  where  it  is  called  the  foefm. 
Here  the  dryness  is  so  great  that  the  danger  of 
fire  in  the  Alpine  villages  is  increased  to  such 
an  extent  that  a  special  fire  watch  has  to  be  set 
during  the  continuance  of  Sifoehn. 

The  weather  of  a  dry  region  is  like  that 
under  a  high,  as  already  described,  and  that  of 
a  wet  region  is  like  that  under  a  low.  They 
need  hardly  be  further  described,  but  there  is 
one  comparison  between  the  two  which  throws 
much  light  on  their  relative  comfort.  It  shows 
why  the  high  temperatures  of  a  dry  climate 
may,  with  proper  dress  and  ventilation,  be 
made  not  only  endurable  but  comfortable. 
Dry  weather  promotes  evaporation  from  the 
surface  of  the  skin.  This  produces  cooling, 
and  the  greater  the  evaporation  the  greater  is 
the  reduction  of  temperature  ;  the  greater  the 
heat  and  the  drier  the  air,  the  more  will  the 
cooling  be.  On  the  other  hand,  the  moister 


LOCAL  INFLUENCES  ON  WEATHER.          201 

the  air  the  less  the  evaporation  and  the  less  the 
cooling.  The  temperature  of  the  skin  under 
these  circumstances,  or  rather  the  temperature 
of  evaporation  which  the  skin  feels,  has  been 
called  the  sensible  temperature.  This  will  be 
the  lower  in  proportion  to  the  dryness  of  the 
air.  If  the  air  is  very  dry  and  hot,  the  reduc- 
tion may  be  twenty  degrees  or  more.  When 
this  happens  the  temperature  of  110°  in  the 
shade,  not  rarely  experienced  in  Arizona  and 
New  Mexico,  may  feel  really  cooler  than  the 
temperature  of  95°  at  New  York. 

Forests  affect  climate  and  the  weather  ma- 
terially. Within  the  forest  are  all  the  effects 
of  shade  and  calm,  as  well  as  the  saving  of 
moisture.  Outside  there  are  also  effects,  though 
they  are  not  such  great  ones.  The  forest  serves 
as  a  wind-break  for  everything  in  its  lee,  and 
if  the  open  areas  are  not  very  large  they  may 
be  as  well  protected  from  the  wind  as  if  in 
the  forest  itself.  Forests  also  reduce,  by  the 
roughness  of  their  surface,  the  speed  of  winds 
that  pass  over  them,  thus  checking  the  violence 
of  the  cyclone  of  which  these  winds  are  a  part. 
They  have  some  effect  on  local  storms  by  con- 
trolling the  heat  of  the  surface  air.  The  differ- 
ences in  these  regards  between  a  forest  and 
an  open  plain  are  well  recognized.  Whether 


202  ABOUT  THE   WEATHER. 

the  forests  also  affect  the  amount  of  the  rain- 
fall, as  is  believed  by  many,  is  not  so  certain. 
It  has  not  yet  been  proved  beyond  the  possi- 
bility of  a  doubt.  That  they  affect  the  way 
the  rain  falls,  however,  can  not  be  doubted. 
In  countries  covered  with  forests  the  storms  of 
very  heavy  rainfall  called  cloud-bursts,  and 
similar  storms,  are  nearly  unknown. 


CHAPTEK  XXYI. 

WEATHER     PREDICTIONS    AS    A    REMEDY    AGAINST 
WEATHER    INJURIES. 

THE  earliest  way  men  had  of  predicting  the 
weather  was  by  what  is  called  the  weather  signs ; 
and  these,  though  sometimes  spurious  and  often 
transported  to  climates  where  they  are  not 
applicable,  may  be  good  and  genuine,  and,  to 
one  who  can  not  see  the  daily  papers  or  who 
loves  to  study  Nature  in  some  of  her  most 
attractive  moods,  they  may  be  of  use  and  in- 
terest. One  of  the  best  known  series  of  pre- 
dictions is  that  of  Dr.  Jenner,  the  genial  and 
accomplished  discoverer  of  the  efficiency  of 
vaccination.  He  described  them  in  verses  that 
were  published  about  a  century  ago.  They  are 
given  here  entire,  as,  with  the  exception  of  the 
rooks,  they  give  a  series  of  signs  useful  in  the 
cooler  and  moister  parts  of  the  United  States. 

THE  SIGNS  OF  RAIN. 

The  hollow  winds  begin  to  blow, 
The  clouds  look  black,  the  glass  is  low ; 
15  203 


204  ABOUT  THE  WEATHER. 

The  soot  falls  down,  the  spaniels  sleep, 
And  spiders  from  their  cobwebs  peep. 
Last  night  the  sun  went  pale  to  bed, 
The  moon  in  halos  hid  her  head ; 
The  boding  shepherd  heaves  a  sigh, 
For  see  !  a  rainbow  spans  the  sky. 
The  walls  are  damp,  the  ditches  smell, 
Closed  is  the  pink-eyed  pimpernel. 
Hark  how  the  chairs  and  tables  crack  ! 
Old  Betty's  joints  are  on  the  rack. 
Loud  quack  the  ducks,  the  peacocks  cry5 
The  distant  hills  are  looking  nigh. 
How  restless  are  the  snorting  swine ! 
The  busy  flies  disturb  the  kine ; 
Low  o'er  the  grass  the  swallow  wings, 
The  cricket,  too,  how  sharp  he  sings ! 
Puss  on  the  hearth,  with  velvet  paws, 
Sits  wiping  o'er  her  whiskered  jaws ; 
Through  the  clear  stream  the  fishes  rise 
And  nimbly  catch  the  incautious  flies ; 
The  glowworms,  numerous  and  bright, 
Illumed  the  dewy  dell  last  night ; 
At  dusk  the  squalid  toad  was  seen 
Hopping  and  crawling  o'er  the  green ; 
The  whirling  dust  the  wind  obeys, 
And  in  the  rapid  eddy  plays ; 
The  frog  has  changed  his  yellow  vest, 
And  in  a  russet  coat  is  dressed ; 
Though  June,  the  air  is  cold  and  still, 
The  mellow  blackbird's  voice  is  shrill ; 
My  dog,  so  altered  in  his  taste, 
Quits  mutton-bones  on  grass  to  feast ; 
And  see  yon  rooks,  how  odd  their  flight ! 
They  imitate  the  gliding  kite, 


WEATHER  PREDICTIONS.  205 

And  seem  precipitate  to  fall, 
As  if  they  felt  the  piercing  ball — 
'Twill  surely  rain— t  see  with  sorrow 
Our  jaunt  must  be  put  off  to-morrow. 

These  are  all  familiar  and  interesting  re- 
actions to  the  increasing  humidity  in  the  at- 
mosphere, and  those  relating  to  things  without 
life  can  be  easily  explained.  Some  slight 
adaptations  must  be  made  for  other  climates, 
and  it  would  be  interesting  for  the  reader  to 
make  them  for  his  own  locality.  The  only 
serious  change  for  the  Northeastern  States  is 
the  cutting  out  of  the  four  lines  about  the 
rooks,  as  we  have  no  bird  here  which  behaves  in 
that  way.  Four  additional  lines  might  be  de- 
voted to  the  uneasiness  and  distress  of  our 
swallows  at  the  approach  of  rain. 

The  sign  which  depends  on  the  glass,  or 
barometer,  is,  of  course,  generally  true,  and  is 
the  mainstay  of  the  predictions  of  sailors,  but 
people  whose  pursuits  keep  them  much  of  the 
time  in  the  open  air,  especially  if  they  are 
affected  by  the  weather,  gradually  acquire  a 
sort  of  unconscious  knowledge  of  coming 
weather  for  a  day  or  more  ahead  which  is 
quite  trustworthy.  The  signs  they  use  appear 
to  be  rather  the  signs  of  the  sky  than  of  the 
earth,  and  are  to  be  found  in  the  appearances 


206  ABOUT  THE  WEATHER. 

and  changes  of  clouds.  Any  one  who  watches 
the  clouds  attentively  will  see  in  them  a 
great  many  trustworthy  indications  of  coming 
weather.  Those  who  live  near  mountains  will 
find  the  study  especially  interesting. 

Another  and  less  satisfactory  attempt  at 
weather  prediction  is  that  which  is  based  on 
the  moon.  This  is  really  astrology,  though 
notwithstanding  its  recent  revival  as  a  fad, 
astrology  proper  has  long  been  thought  dead. 
Astrological  principles  lie  at  the  foundation  of 
the  predictions  of  the  popular  weather  prophets 
as  published  in  almanacs.  Of  these  there  are 
several  which  have  quite  a  following  for  rea- 
sons that  are  not  easy  to  understand.  Such 
predictions  are  really  of  no  use,  for  they  are 
not  right  often  enough  to  permit  one  to  lay 
plans  by  them.  We  are  unable  to  prove  that 
any  heavenly  body  except  the  sun,  its  prime 
mover,  has  an  appreciable  effect  on  the  weather. 
The  moon  has  no  influence  worth  taking  into 
account. 

It  is  the  methods  of  modern  science 
which  have  enabled  us  to  predict  the  weather 
with  an  accuracy  great  enough  to  be  of 
some  use.  The  two  fundamental  principles 
of  modern  science  are  that  of  the  whirl  or 
cyclone  and  anticyclone,  and  that  of  the  east- 


WEATHER  PREDICTIONS.  207 

erly  drift   of  the   weather   in   the   temperate 
zones. 

Predictions  are  based  on  the  weather  map, 
a  specimen  of  which  is  given  on  page  208% 
Isotherms,  dotted  (broken)  lines,  are  drawn  for 
each  ten  degrees.  The  isobars  are  solid  lines, 
drawn  for  each  tenth  of  an  inch.  Shaded  areas 
indicate  regions  of  precipitation  during  the  pre- 
ceding twenty-four  hours.  The  arrows  fly  with 
the  wind,  and  the  circles  have  the  following 
meaning : 

O  Clear.   3  Partly  cloudy.  0  Cloudy.  ©  Rain.   ©  Snow. 

Now,  the  cyclones  are  for  that  date  and  hour 
at  the  words  LOW,  and  the  anticyclones  at 
the  words  HIGH.  .  The  prediction  consists  in 
foreseeing  how  far  these  centers  will  advance 
in  the  next  thirty-six  hours,  what  direction 
they  will  take,  and  how  much  change  may  be 
undergone  by  them  and  by  the  intermediate 
weather.  In  general,  the  weather  will  shift 
forward  on  the  map  about  seven  hundred  and 
fifty  miles  in  that  time. 

If  the  reader  will  imagine  the  centers  of 
pressure  to  have  advanced  this  distance  and  to 
carry  their  weather  with  them,  he  will  have 
made  a  genuine  prediction,  though  perhaps  not 
an  accurate  one.  Experienced  forecasters  are 


Of    TH£ 


WEATHER  PREDICTIONS.  209 

entitled  to  a  grade  of  ninety  per  cent  on  the 
accuracy  of  their  predictions. 

The  work  of  observation,  collection,  tabula- 
tion, and  map-making  is  done  by  a  weather 
service.  In  the  United  States  this  employs 
several  hundred  men,  and  costs  over  a  million 
dollars  a  year.  There  are  perhaps  a  score  of 
other  weather  services  covering  the  civilized 
countries  generally  in  the  world,  but  the  Amer- 
ican is  the  largest  and  on  the  whole  makes 
the  best  forecasts.  It  is  also  by  far  the  most 
expensive  ;  this  is  due  both  to  the  area  it  covers 
and  to  the  perfection  of  its  work. 

The  chief  difficulty  of  the  weather  service, 
after  all,  is  to  be  sure  that  its  warnings  will 
reach  those  most  interested — the  farmer  and  the 
transportation  managers.  The  warnings  are 
published  in  the  daily  papers,  but  are  only 
for  the  day  ahead,  and  so  do  not  continue  long 
of  value.  The  readers  of  the  daily  papers  are 
very  numerous,  but  the  list  does  not  include 
most  farmers  nor  many  engaged  in  marine 
commerce.  Those  engaged  in  land  commerce 
can  be  easily  reached  in  several  ways,  the 
others  only  with  difficulty  in  the  short  time 
during  which  the  prediction  runs.  Various 
ingenious  devices  have  been  invented,  and  some 
tried  ;  but  no  satisfactory  means  have  yet  been 


210  ABOUT  THE  WEATHER. 

found  of  reaching,  in  time,  the  farmer  more 
than  two  miles  from  a  town  on  the  railway,  or 
a  seaman  not  near  port.  The  first  part  of  the 
problem  is  being  solved  by  the  extension  of  the 
telephone  and  the  free  delivery  of  mail  over 
the  rural  districts,  the  latter  service  having  ex- 
perienced a  marvelous  development  in  the  last 
few  years.  With  wireless  telegraphy  and  other 
improved  means  it  may  be  that  satisfactory 
communication  can  soon  be  extended  at  sea. 

The  prediction  of  the  weather,  though 
abundantly  accurate,  solves  only  in  part  the 
problem  of  wreather  protection.  The  warnings 
must  reach  the  sufferer  in  time  to  save  him. 
Even  then  the  protection  is  not  complete,  for  the 
recipient  must  know  how  to  protect  himself 
when  forewarned.  Because  he  knows  a  flood  is 
due  the  next  day,  it  does  not  follow  that  he 
can  move  his  house  out  of  harm's  way.  Prob- 
ably man  will  never  be  able  to  evade  or  escape 
the  weather  completely.  But  what  he  can  do 
will  depend  on  his  knowledge,  and  the  knowl- 
edge he  will  most  need  for  this  purpose  is  that 
of  the  weather  itself.  The  history,  present 
state,  and  prospects  of  the  science  of  the 
weather  we  will  sketch  briefly  in  the  next 
chapter. 


CHAPTEK  XXVII. 

THE    PROGRESS    OF    KNOWLEDGE    OF   THE 
WEATHER. 

THERE  is  perhaps  nothing  which  has  been 
more  talked  about  to  less  purpose  than  the 
weather.  The  first  real  step  toward  any  scien- 
tific knowledge  of  the  weather  was  in  the  in- 
vention of  the  barometer  nearly  three  centu- 
ries ago.  Accurate  observations  with  it  soon 
began,  and  observations  on  the  temperature, 
wind,  and  rain  rapidly  followed,  but  the  key 
to  the  series  was  not  discovered,  and  the  ob- 
servations were  collected  in  myriads  all  over 
the  earth  to  almost  very  little  purpose.  This 
is  true  so  far  as  weather  was  concerned ;  as  to 
climate,  these  observations  had  given  much  in 
formation,  and  this  is  condensed  and  shown  in 
the  better  maps  of  the  climate  of  the  earth. 

It  was  not  until  the  happy  idea  of  taking 
simultaneous  observations  at  places  far  apart 
had  been  put  into  practice  that  further  light 
was  thrown  on  the  problems  of  the  weather. 

211 


212  ABOUT  THE  WEATHER. 

This  was  done  first— in  the  States  at  least — by 
Thomas  Jefferson,  who  afterward  became  Presi- 
dent of  the  United  States.  He  w^as  an  accom- 
plished and  many-sided  man,  and  was  always 
interested  in  meteorology.  When  at  the  Consti- 
tutional Convention  in  Philadelphia  he  pro- 
vided himself  with  a  thermometer,  with  which 
he  took  observations  wherever  he  went,  record, 
ing  them  in  his  private  papers.  While  living 
at  Monticello,  near  the  University  of  Virginia, 
which  he  founded,  and  which  still  remains  a 
unique  and  useful  institution,  he  prevailed  on 
Bishop  Madison,  who  lived  near  Norfolk,  across 
the  great  State  of  Virginia,  to  take  with  him 
simultaneous  observations  with  the  barometer. 
This  did  not  continue  long,  and  the  next 
real  step  in  advance  occurred  a  generation 
later  by  those  who  undertook  to  study  the 
destructive  hurricanes  of  the  West  Indies. 
They  made  as  perfect  weather  maps  as  they 
could,  and  soon  discovered  both  the  great  facts 
that  the  storms  are  whirls,  and  that  they  move 
eastward.  A  great  controversy  raged  about 
these  discoveries,  and  they  were  in  time  veri- 
fied, but  nothing  could  be  done  in  weather 
prediction  until  the  telegraph  was  invented 
and  used.  This  came  some  years  later,  and 
Morse  was  occupied  for  years  in  getting  it  into 


PROGRESS  OF  KNOWLEDGE  OF  THE  WEATHER.     213 

use.  The  interest  in  the  weather  controversy 
was  so  great  that  the  telegraph  was  expected 
to  be  chiefly  useful  in  enabling  the  weather  to 
be  predicted.  Few  seem  to  have  anticipated 
its  enormous  value  in  general  commerce  and  in 
the  collection  of  news. 

After  the  telegraph  had  been  extended  to 
distant  parts  of  the  country,  it  w^as  employed 
by  Professor  Henry  to  get  material  for  a  daily 
weather  map  which  he  had  prepared  and  posted 
in  the  Capitol  at  Washington.  The  civil  war 
soon  interrupted  this  work,  and  it  was  not  re- 
sumed until  1870,  when  Professor  Abbe  began 
it  with  the  aid  of  the  Western  Union  Tele- 
graph Company,  with  center  at  Cincinnati. 
Between  Professor  Henry's  attempt  and  that 
of  Professor  Abbe,  weather  prediction  had  been 
undertaken  by  several  foreign  governments. 
By  the  latter  part  of  1870  it  w^as  engaged  in 
the  United  States  Government  under  the  direc- 
tion of  General  Myer,  of  the  army.  Since  then 
weather-map  making  has  spread  over  the  civil- 
ized world  and  developed  slowly  in  usefulness. 
The  chief  advance  has  been  in  the  development 
of  the  instruments  which  are  now  very  perfect, 
and  register  results  continuously  and  automati- 
cally, so  that  the  weather  for  any  moment  can 
be  ascertained.  The  only  element  not  thus 


214  ABOUT  THE  WEATHER. 

registered  is  the  moisture  of  the  air,  and  this  is 
still  imperfectly  observed,  though  it  is  of  great 
importance. 

There  are  three  lines  in  which  advance  has 
been  attempted  and  is  still  going  on.  The  first 
is  that  of  the  weather  of  the  polar  regions.  A 
better  knowledge  of  this  is  necessary,  because 
the  atmosphere  is  one  great  machine,  and  what 
happens  in  one  part  of  it  is  dependent  to 
some  degree  on  what  happens  elsewhere.  Great 
expenditure  of  money  and  of  human  effort 
and  life  has  been  made  to  perfect  our  knowl- 
edge of  polar  weather.  One  of  the  most  not- 
able of  these  attempts  was  the  daring  but 
disastrous  one  conducted  by  General  Greely  to 
Lady  Franklin  Bay  in  the  high  north.  With 
our  present  experience,  life  in  an  arctic  winter 
has  become  safer,  and  we  have  reason  to  hope 
that  the  necessary  knowledge  of  this  sort  will 
soon  be  provided. 

The  next  field  of  weather  exploration  to 
be  undertaken  was  that  of  the  upper  air.  We 
are  down  to  the  bottom  of  the  aerial  ocean, 
where  it  is  not  easy  to  take  observations  of 
any  considerable  elevations  except  the  clouds. 
There  has  been  an  attempt  to  fill  this  vacancy 
of  knowledge  by  observatories  on  high  moun- 
tains. These  have  now  all  been  abandoned  in 


PROGRESS  OF  KNOWLEDGE  OF  THE  WEATHER.     215 

the  United  States  to  the  great  regret  of  stu- 
dents of  the  weather  all  over  the  world,  but 
such  observatories  are  maintained  in  many  for- 
eign countries.  The  work  is  also  done  by  bal- 
loons, and  regular  balloon  weather  observations 
have  been  extensively  carried  on.  In  the 
United  States  Prof.  Henry  A.  Hazen  is  the 
most  persistent  and  daring  of  observers  from 
balloons.  Investigations  of  the  weather  are 
also  supplemented  by  observations  with  regis- 
tering instruments  carried  up  by  kites,  and,  as 
the  art  of  kite-flying  improves,  these  prove 
more  and  more  useful.  Systematic  observa- 
tions with  balloons  and  kites  will  soon  give  us 
a  great  deal  of  light  on  the  phenomena  of  the 
weather. 

There  are  two  planes  of  activity  in  natural 
wTeather-making — the  surface  of  the  earth  and 
the  cloud  layer.  For  ordinary  weather  the 
earth's  surface  is  probably  the  more  active ;  but 
the  origin  of  the  intense,  and  therefore  most 
important  and  most  destructive,  storms  seems 
to  be  above. 

The  third  line  of  advance  in  weather  lore  is 
in  the  prediction  of  the  weather  for  seasons. 
This  has  been  attempted  in  many  ways,  and 
there  appear  to  be  two  in  which  there  has  been 
a  slight  degree  of  success.  The  one  depends  on 


216  ABOUT  THE  WEATHER. 

the  activity  of  the  sun,  as  shown  chiefly  in  the 
presence  or  absence  of  sun  spots.  There  is  un- 
doubtedly a  general  difference  in  the  weather 
for  different  parts  of  the  sun-spot  cycle,  but 
this  difference  varies  in  different  parts  of  the 
earth's  surface.  Such  predictions  promise  little 
beyond  general  results,  such  as  good  harvests  or 
bad  ones,  much  rain  or  little,  more  local  storms 
or  less,  and  so  on. 

Rather  more  hopeful  is  the  prediction  of 
the  seasons  in  regions  where  regular  monsoons 
occur,  as  in  India.  In  such  places  the  con- 
ditions during  one  monsoon,  and  especially  the 
amount  of  snow  on  the  mountains  in  winter, 
are  believed  to  be  a  fair  indication  of  the 
next  season.  Some  success  is  claimed  in  India 
for  such  predictions. 

A  number  of  interesting  experiments,  be- 
ginning as  far  back  as  February  4,  1891,  have 
been  and  are  being  made  in  weather  prophecy 
by  the  aid  of  gas  balloons,  and  of  fire  balloons, 
and,  as  has  been  noted,  of  kites ;  these  experi- 
ments promise  valuable  results. 

In  the  use  of  kites,  Mr.  William  A.  Eddy, 
the  experimenter,  writes  : 

"The  principal  obstacles  which  remain  to 
be  overcome  are  dead  calms  and  the  sudden 
rush  of  thunder  showers. 


PROGRESS  OF  KNOWLEDGE  OP  THE  WEATHER.     217 

"The  conditions  of  thunderstorm  prophecy 
are  peculiar  in  that  while  these  storms  may  be 
extremely  local,  they  at  the  same  time  form 
themselves  into  a  more  or  less  unbroken  line 
of  five  hundred  or  one  thousand  miles  in  length, 
advancing  rapidly,  but  in  the  form  of  a  vast 
line  of  battle.  This  line  of  local  storms  is  at 
times  broken  by  irregular  motions,  and  by 
storms  that  seem  to  go  around  certain  regions. 
There  is  no  doubt  that  electrical  observations 
with  my  kite-sustained  copper  wire  will  de- 
termine whether  a  thunderstorm  is  approach- 
ing, receding,  or  simply  circling  around  at  an 
equal  distance  from  the  center  of  observation. 

"  A  copper  wire  fastened  to  a  rectangular 
frame  coated  with  tinfoil  is  raised  into  the  air 
suspended  from  the  kite  string.  Electric 
sparks  are  then  drawn  to  an  iron  spike,  driven 
into  the  ground,  and  the  length  of  the  spark 
gap  is  measured.  The  presence  of  thunder- 
storm conditions  is  indicated  by  the  fact  that 
sparks  begin  before  the  tinfoil  collector  has 
reached  a  height  of  much  more  than  one  hun- 
dred feet.  The  thunderstorm  may  be  miles 
away  or  far  beyond  the  horizon,  yet  its  influ- 
ence, like  that  of  a  coil  spark  in  wireless  teleg- 
raphy, is  revealed  by  the  abnormal  frequency 
and  brilliance  of  the  sparks  drawn  from  my 


218  ABOUT  THE  WEATHER. 

electric  wire  reaching  from  a  high  point  on  the 
kite  string  down  into  the  earth  through  the 
iron  spike,  which  draws  the  spark. 

"During  the  great  kite  ascensions  at  Blue 
Hill  Observatory,  near  Boston,  where  about  five 
miles  of  steel  wire  was  paid  out  upward,  sus- 
tained by  kites,  reaching  the  greatest  kite  alti- 
tudes ever  attained,  it  was  found  that  some 
clouds  are  invisible,  but  are  revealed  by  the 
humidity  apparatus  passing  through  them. 
Since  1892,  during  hundreds  of  observations,  I 
had  noticed  that  the  approach  of  clouds  over- 
head when  the  kite-sustained  copper  wire  was 
aloft  invariably  caused  an  increase  in  the  length 
of  sparks  drawn  from  the  kite  wire,  while  the 
recession  of  the  cloud  caused  a  marked  diminu- 
tion in  the  spark  length.  During  an  evenly 
clouded  sky  the  sparks  were  steady,  while  dur- 
ing a  clear  sky  the  sparks  were  smaller,  but 
also  steady.  The  sparks  increase  in  length  with 
increased  height  under  all  circumstances,  but 
they  vary  greatly  with  cloudiness.  The  rela- 
tion of  kite  electricity  to  local  storms  was 
shown  during  a  passing  squall,  when  the  elec- 
tric sparks  crackled  from  the  kite  wire  to  the 
iron  spike  in  an  almost  incessant  stream.  But 
as  soon  as  the  air  began  to  clear  not  a  spark 
could  be  drawn  until  I  had  sent  the  collector 


PROGRESS  OF  KNOWLEDGE  OF  THE  WEATHER.    219 

to  twice  its  previous  altitude,  and  even  then 
the  sparks  were  faint.  Had  I  tripled  the 
height  of  the  collector,  the  sparks  would  have 
come  again  as  before,  but  the  experiment 
showed  that  probably  more  than  two  thirds  of 
the  electricity  had  been  dissipated  by  the  pass- 
ing storm,  while  in  advance  of  the  storm  the 
electricity  was  in  full  force.  The  extent  of 
the  electrical  excitement  of  the  kite  wire  is  in 
proportion  to  the  intensity  of  the  storm,  and  as 
the  storm  passes  away  instead  of  lessening  two 
thirds  of  the  electricity  there  may  be  a  decrease 
of  seven  eighths. 

"When  a  thunderstorm  approaches  with- 
in twenty  miles  of  the  kites  I  may  get  more  elec- 
tric force  with  my  electric  collector  at  a  height 
of  one  hundred  feet  than  I  would  obtain  after 
the  storm  had  passed  with  my  electric  collector 
at  a  height  of  eight  hundred  feet.  I  have  not 
yet  left  my  kite  electric  apparatus  aloft  during 
a  passing  thunderstorm.  The  lightning  would 
be  almost  certain  to  strike  so  good  a  conductor 
as  a  kite-sustained  copper  wire,  and  the  rush  of 
wind  in  advance  of  such  a  storm  would  destroy 
the  strongest  kite  ever  made,  or  break  the  kite 
cable. 

"  Marconi  has  shown  us  that  sparks  radiate 
force  to  great  distances,  depending  on  the  height 

16 


220  ABOUT  THE  WEATHER. 

from  which  the  sparks  emanate.  The  electric 
force  of  the  coil-spark  in  wireless  telegraphy  is 
of  a  lower  tension  and  different  wave-length 
from  that  in  atmospheric  electricity,  yet  it  is 
obvious  that  the  lightning  flash  may  cause 
effects  at  vastly  greater  distances  than  any  cov- 
ered by  the  tamer  electricity  manufactured 
artificially,  unless  we  consider  the  wonderful 
high-tension  electric  forces  handled  by  Tesla. 
The  forecasts  of  the  approach  of  thunder- 
storms which  are  hundreds  of  miles  away  are 
indicated  at  Bayonne  by  the  flashing  of  the 
kite  wire,  and  part  of  the  work  which  I  am 
carrying  on  is  to  attempt  to  locate  the  exact 
distance  of  the  thunderstorm  within  a  few 
miles,  as  the  ocean  cable  experts  now  locate 
the  exact  point  in  the  break  in  an  ocean  cable. 
"  The  hot-air  or  gas  balloon,  operated  in  co- 
operation with  Professor  Langley,  of  the  Smith- 
sonian Institution,  is  also  a  valuable  weather 
prophet  at  times  when  kites  can  not  be  flown, 
owing  to  dead  calms,  and  when  there  is  no 
time  to  inflate  and  send  aloft  a  ponderous 
balloon  with  a  man  suspended  below  it.  I  am 
as  yet  almost  without  data  obtained  during  a 
dead  calm.  On  April  25,  1899, 1  sent  up' my 
first  hot-air  balloon  in  a  light  wind,  with  a  self- 
recording  thermometer  suspended  about  twelve 


PROGRESS  OF  KNOWLEDGE  OF  THE  WEATHER.     221 

feet  below  it,  at  8:15  p.  m.  The  earth  tem- 
perature was  69°,  while  the  temperature  aloft 
was  66°,  a  fall  of  3°.  The  hot  air  in  the  balloon 
seemed  to  have  no  effect  on  the  thermometer, 
because  the  hot  air  and  smoke  ascended  twelve 
feet  ahead  of  the  thermometer,  and  when  the 
balloon  began  to  fall  the  hot  air  issuing  from 
it  still  ascended. 

"  Electric  wire  tests  will  also  soon  be  made 
with  this  balloon  as  well  as  tests  of  wireless 
telegraphy. 

"  The  most  marked  advance  which  I  have 
recently  made  in  kite  electricity  is  to  send  aloft 
a  Ley  den  jar,  suspended  from  the  kite  cable. 
Electric  sparks  were  drawn  from  the  jar  when 
it  was  within  sixty  feet  of  the  earth,  and  pow- 
erful brush  lights  formed  with  a  hissing  sound 
when  the  terminals  were  four  inches  apart. 
This  will  enable  me  to  measure  the  distance  of 
a  thunderstorm  with  much  greater  accuracy 
and  without  the  use  of  very  expensive  and  deli- 
cate instruments.  The  thermometrical  tests  of 
the  upper  air  are  still  actively  under  way  at 
Blue  Hill  Observatory,  at  Bayonne,  and,  so 
far  as  known,  at  Washington,  D.  C.,  and  at  the 
sixteen  kite  observation  stations  established  by 
the  Weather  Bureau  in  the  central  West.  The 
European  meteorological  observatories  are 


222  ABOUT  THE  WEATHER. 

rapidly  being  equipped  with  kites,  as  pointetd 
out  by  A.  L.  Rotch,  director  and  founder  of 
Blue  Hill  Observatory.  Reports  of  the  kite 
observations  in  Europe  and  by  the  Weather 
Bureau  are  still  pending,  and  thousands  of  kite 
observations  in  all  parts  of  the  w^orld  Avill 
doubtless  soon  be  classified,  when  I  hope  to 
have  the  honor  of  presenting  still  later  facts. 
Meantime,  my  experiments  at  Bayonne  will 
continue  along  new  and  difficult  lines  of  inves- 
tigation." 


CHAPTEK  XXYIII. 

EXPERIMENTING    WITH    THE    AIR. 

THERE  is  great  pleasure  and  much  informa- 
tion to  be  gained  by  experimenting  for  one's 
self  in  any  of  the  sciences.  It  is  much  better 
than  studying  books,  though  the  latter  is  neces- 
sary to  show  one  what  to  look  for  and  how  to 
look  for  it.  Such  experiments  make  what  is 
called  the  laboratory  method  in  teaching,  and 
they  teach  the  student  very  thoroughly  and 
tell  him  many  things  that  the  books  fail  to 
teach.  Learning  through  the  eye  and  the  hand 
is  more  thorough  and  more  attractive  than 
learning  from  books.  The  atmosphere  offers 
very  many  ways  of  learning  in  this  manner, 
and  what  it  teaches  us  is  of  great  use  in  every* 
day  life ;  it  teaches  one  to  understand,  and 
watch,  and  take  an  intelligent  interest  in  the 
great  panorama  of  the  weather  which  is  con- 
stantly unrolling  before  us. 

Studies  of  the  atmosphere  and  its  changes 
may  be  carried  on  in  three  different  ways. 

233 


224  ABOUT  THE  WEATHER. 

One  is  by  making  simple  instruments  and  seeing 
what  they  will  tell  us  ;  the  other  is  by  watch- 
ing what  goes  on  about  us  and  by  trying  to  ex- 
plain it.  The  first  is  the  way  of  experiments, 
the  second  that  of  general  observation. 
A  third  way  is  to  buy  the  excellent 
instruments  used  by  meteorologists 
and  to  take  regular  observations  with 
them.  In  this  chapter  we  will  de- 
scribe some  simple  instruments  which 
can  be  easily  made,  and  experiments 
which  can  be  conducted  with  them. 

The  toy  rubber  balloon  is  a  very 
fair  barometer,  and  if  it 


FIG.  44.— Toy  balloon  ba-     could  be  made  so  that  it 

rometer. 

would  not  leak  gas  it 
would  be  an  excellent  one.  If  a  cord  or  light 
long  chain  is  attached  to  one  of  these  balloons 
so  as  to  keep  it  three  or  four  feet  from  the 
floor,  with  a  long  string  lying  on  the  floor, 
then  when  the  pressure  rises  the  balloon  will 
rise,  and  will  sustain  a  greater  length  of  twine  ; 
when  it  falls,  tKe  balloon  will  descend  and 
the  length  of  the  cord  will  be  shorter.  The 
observation  is  made  by  measuring  the  length  of 
the  cord  between  the  floor  and  balloon,  or  the 
height  of  the  balloon  from  the  floor.  The  bal- 
loon will  lose  gas  more  slowly  if  it  is  varnished. 


EXPERIMENTS  WITH  THE   AIR. 


225 


Another  arrangement  for  the  pressure  of 
the  air  was  patented  many  years  ago,  and  is 
very  simple.  It  is  a  long  pole,  carefully  bal- 
anced with  a  small  heavy  weight  at  one  end 
and  a  much  larger  and  lighter  one  at  the 
other.  The  heavy  weight  may  be  a  piece  of 
lead,  the  lighter  a  closed  tin  box.  This  simple 
device  plays  up  and  down  with  changes  in 
air  pressure ;  the  larger  weight  being  up  when 
the  air  pressure  is  high,  and  down  when  the 
pressure  is  low.  The  more  probable  the  storm 
the  lower  the  larger  end  will  be.  If  this  end  is 
painted  white  and 
is  large  it  can  be 
seen  at  a  distance. 

The  experi- 
menter can  easily 
make  a  simple  ba- 
rometer at  little 
expense.  A  glass 
tube,  three  feet 
long,  with  a  bore 
about  the  size  of 
a  lead  pencil  with  one  end  closed  must  be  pro- 
vided. This  tube  should  be  carefully  cleaned 
and  dried  inside,  filled  with  mercury  and,  with 
the  finger  on  the  open  end,  turned  down,  thrust 
into  a  small  glass  jar  or  bottle  of  mercury,  and 


FIG.   45. 


226 


ABOUT  THE  WEATHER. 


the  finger  removed 
six  or  eight  inches, 


FIG.  46.— The  mercurial 
barometer.  The  glass 
tube  held  on  the  right 
hand  is  closed  at  B. 
It  is  reversed  in  a 
basin  of  mercury  on 
the  left  hand  and  the 
mercury  in  the  tube 
falls  to  n,  at  which 
point  it  is  sustained 
by  the  pressure  of  the 
air  on  the  surface  of 
the  mercury  in  the  ba- 
sin. The  space  above 
n  is  a  vacuum. 


,  The  mercury  will  descend 
and  the  barometer  is  made. 
It  must  then  be  fastened  se- 
curely, and  a  three-foot  scale 
placed  behind  it,  with  the 
end  even  with  the  surface 
of  mercury  in  the  bowl. 
The  top  of  the  column  of 
mercury  rises  and  falls  with 
the  pressure. 

A  similar  barometer  can 
be  made  of  water,  but  it  will 
have  to  have  a  tube  thirty- 
six  feet  long  above  the  sur- 
face. Besides,  the  water  will 
evaporate  and  change  the 
readings.  So  large  a  barom- 
eter would  attract  attention, 
and  the  changes  in  it  would 
be  measured  by  feet  instead 
of  inches. 

Glycerin  could  be  used 
instead  of  water,  and  this 
would  not  evaporate.  The 
glycerin  would  be  so  much 
lighter  than  the  mercury  that 
the  tube  would  have  to  be 
twenty-six  feet  long.  It  is 


EXPERIMENTS   WITH  THE  AIR.  227 

expensive  to  make  and  to  erect  after  the  mate- 
rial is  obtained.  The  expense  could  be  less- 
ened by  having  all  the  tubes  of  metal,  except 
the  last  six  or  eight  feet,  which  should  be  of 
glass.  An  inch  of  change  in  a  mercurial  ba- 
rometer would  here  make  nearly  a  foot.  It 
could  be  erected  on  the  stairway  or  in  the  va- 
cant central  space  often  found  in  large  school 
and  other  buildings,  and  would  make  the 
changes  in  the  pressure  of  the  air  very  plain 
and  easy  to  see. 

An  interesting  thermometer  can  be  made 
by  fastening  together  two  strips  of  materials 
differing  greatly  in  their  expansion  when 
heated.  Whalebone  or  hard  rubber  could  form 
one  of  the  strips  and  steel  the  other.  If  these 
are  fastened  firmly  together,  the  combined  strip 
will  bend  toward  the  steel  when  colder  and 
away  from  it  when  warmer.  The  apparatus  is 
sometimes  used  to  regulate  temperature  in  in- 
cubators and  other  places  where  this  must  be 
kept  very  even.  They  are  so  placed  that  they 
close  the  draft  when  the  temperature  is  too 
high  and  open  it  when  too  low.  A  suitable 
one,  large  enough,  could  be  put  on  the  furnace 
of  a  dwelling.  It  may  be  made  capable  of 
raising  a  heavy  draft  door  or  valve. 

A  toy  windmill  may  be  used  for  measuring 


228  ABOUT  THE  WEATHER. 

the  speed  of  the  wind  if  some  way  is  added 
for  counting  the  number  of  revolutions.  This 
can  be  done  by  having  a  very  small  spool  on 
the  axis  of  the  mill  on  which  is  wound  up 
thread  from  a  very  large  spool  carrying  a 
pointer.  A  much  better  way,  but  more  diffi- 
cult to  make,  would  be  a  set  of  cogs  with  two 
pointers,  one  for  single  revolutions,  the  other 
for  hundreds,  and  perhaps  a  third  for  thou- 
sands, like  the  counters  on  a  gas  meter.  The 
number  of  revolutions  for  a  mile  of  wind  could 
be  had  by  carrying  the  mill  on  a  flat  car  on  a 
railway  train  for  a  known  distance.  The  mill 
must  work  very  easily  and  smoothly  to  turn 
for  gentle  winds.  It  should  be  carried  on  a 
wind  vane,  in  order  to  always  be  faced  to  the 
wind. 

There  are  very  many  ways  of  roughly  get- 
ting the  signs  of  change  in  the  moisture.  One 
is  by  dry  common  salt,  which  absorbs  it  and 
becomes  damp,  increasing  in  weight  as  the 
moisture  increases. 

A  better  way  is  to  use  a  long,  smooth  hair, 
for  hair  has  great  capacity  for  absorbing  moist- 
ure. It  increases  in  length  when  the  air  grows 
more  moist,  and  shortens  when  it  is  dry.  The 
human  hair  is  excellent  for  this  purpose.  A 
long  hair  should  be  selected  and  carefully 


EXPERIMENTS  WITH  THE  AIR. 


229 


washed  several  times  in  weak  ammonia  to  take 
out  the  oil.  It  should  then  be  suspended 
at  one  end,  passed  several  times  around  a  spool, 
as  in  the  diagram,  and  weighted  at  the  other 
to  keep  it  taut.  The  spool  should  turn  very 
easily,  and  as  the  hair  lengthens  or  shortens  it 
will  turn  forward  and  back.  If  it  carries  a 
pointer  and  scale,  the  turns  can  be  observed, 
and  the  grades  will  be  from 
dry  to  wet.  This  is  the  hair 
hygrometer,  and  delicate  ones 
can  be  bought  which  will 
serve  very  well  the  purpose 
intended. 

The  toy  which  represents 
a  dancing   girl,  the  color  of 
whose  clothing  changes  from 
blue  to  pink  as  the  air  grows 
more  moist,  or  back  again  as 
it  grows  drier,  is  an  interest-  Fia.47.-Hairhygrom. 
ing   weather    predicter.       It 
depends    on   certain   chemicals  which   change 
color   with    their   gain    or   loss    of    moisture. 
Among  these  is  the  chloride  of  cobalt. 

Wedgewood,  the  celebrated  pottery  maker, 
constructed  a  toy  of  a  different  sort,  which, 
however,  depended  on  the  moisture  of  the  air 
for  its  action.  It  was  a  small  wooden  horse, 


230  ABOUT  THE  WEATHER. 

with  points  on  its  feet  directed  backward. 
This,  when  left  undisturbed,  gradually  made 
its  way  across  a  room.  When  the  air  wTas  moist 
it  lengthened,  and  the  fore  feet  advanced ; 
when  the  air  was  drier  it  shortened,  and,  the 
fore  feet  being  held  by  the  points,  the  hind  feet 
were  drawn  up  toward  it.  Thus  with  each 
change  in  the  moisture  of  the  air  it  made  a 
step  forward,  and  in  time  completed  a  passage 
across  the  room. 

The  heat  can  make  so  heavy  an  object  as  a 
rail  of  railway  iron  travel  in  the  same  way  if 
there  is  a  point  fixed  to  each  end,  both  set 
in  the  same  direction.  Each  hot  summer  day 
makes  it  reach  out  a  little  forward,  and  the 
following  cool  night  makes  it  contract :  and  the 
summer's  progress  is  not  inconsiderable. 

The  rapidity  of  evaporation  is  another 
means  of  testing  the  dryness  of  the  air.  This  is 
not  easy  to  test,  for  the  evaporation  varies  with 
the  weather,  with  the  supply  of  water,  and 
also  with  the  character  and  colors  of  the  ma- 
terial from  which  evaporation  occurs — soil,  sur- 
face, dead  leaves,  and  so  on.  A  very  simple 
and  useful  evaporation  instrument  giving  good 
results  from  day  to  day  is  that  proposed  by 
Piche.  It  is  made  by  filling  a  test  tube  with 
water,  placing  a  little  circle  of  blotting  paper 


EXPERIMENTS  WITH  THE  AIR. 


231 


on  the  top,  reversing  with  a  clamp  on  the  paper, 
as  in  the  picture.  It  is  then  to  be  fastened  up 
by  a  wooden  clamp,  so  that  it  will 
stand  erect.  The  measurement  con- 
sists in  taking  the  height  of  the  col- 
umn of  water,  a,  from  time  to  time. 
The  decrease  is  due  to  water  evapo- 
rated from  the  wet  surface,  &,  since 
the  last  observation.  If  two  such  ar- 
rangements, or  evaporimeters,  are  used 
they  must  be  as  nearly  alike  as  pos- 
sible, so  that  they  will  give  results 
that  can  be  compared. 

There   are   many  other  simple   de- 
vices for   showing  and  measuring   the 
changes  in  the  elements  of  the  weather, 
but   these   are   enough    to   show   how 
they   may   be    made    and  what    sorts 
of   experiments   they   will   per- 
mit.    An  ingenious  person  will 
think   of    many   others.     Their 
value  lies  chiefly  in  making  one 
familiar  with  the  changes  constantly  going  on  in 
the  air,  though  invisible  except  for  their  effects. 


FIG.  48.— Piche's 
evaporimeter. 


CHAPTEE  XXIX. 

SIMPLE    RESULTS    OF    WEATHER    CHANGES. 

THE  changes  in  the  humidity  of  the  air 
are  fertile  in  producing  changes  in  the  familiar 
objects  with  which  the  reader  is  surrounded. 
Wood,  especially  when  not  varnished  or 
oiled,  absorbs  moisture  readily.  The  result  is 
that  the  joints  of  furniture  swell  when  the 
moisture  is  increasing,  and  chairs  and  tables 
creak  and  give  out  the  loud  reports  often 
heard  in  a  house.  The  catgut  strings  of  musi- 
cal instruments  moisten  and  lengthen,  and  thus 
get  out  of  tune.  Doors  and  windows  swell, 
and  are  hard  to  open  or  close.  The  down  of 
the  dandelion  contracts.  Fir  cones  hung  up  in 
the  house  where  the  air  passes  them  freely,  close 
their  scales  against  wet  weather  and  open  again 
for  dry,  and  the  same  thing  happens  for  the 
prickles  of  the  teasel.  A  piece  of  kelp  or  sea- 
weed absorbs  moisture  so  readily  that  it  be- 
comes damp  before  rain.  The  strings  of  a 
spider's  web  become  lax  in  moist  weather,  but 


SIMPLE  RESULTS  OF  WEATHER  CHANGES.     233 

tighten  up  when  it  dries.  Gossamer  and  light 
seeds  with  plumes,  like  the  thistle  seeds,  fly 
when  the  air  is  dry,  but  gradually  subside  as 
it  becomes  more  moist.  Absorptive  salts  and 
chemicals  imbibe  moisture,  and  some  of  them 
become  so  wet  as  to  be  half  liquid.  Thirsty 
plants  also  take  in  moisture,  and  in  hot  weather, 
when  the  plants  are  becoming  lax  and  drooping 
from  lack  of  sufficient  water,  the  increasing 
moisture  causes  them  to  fill  out  and  stiffen 
again  without  any  visible  reason  for  the  change. 

The  sweating  of  walls  and  stones  is  a  sign 
of  the  same  sort.  This  is  a  real  dew,  and  when 
abundant  indicates  also  that  the  winter's  cold 
still  remains  in  the  walls.  In  climates  where 
changes  in  moisture  are  very  great,  special  pro- 
vision has  to  be  made  against  the  sweating  of 
walls.  Under  such  conditions  even  the  great 
lens  of  a  telescope  may  have  so  much  moisture 
deposited  on  it  as  to  interfere  with  the  work  of 
the  astronomer.  The  increase  of  dew  proper 
is  also  an  indication  of  this  increase  of  moisture, 
and  this  is  one  of  Nature's  ways  to  feed  plants 
where  the  rain  may  be  insufficient. 

The  change  in  quantity  of  moisture  also 
changes  the  qualities  of  the  air.  The  sun's 
rays  are  more  easily  trapped  by  moisture  than 
by  dry  air,  and  consequently  they  do  not  seem 


234  ABOUT  THE  WEATHER. 

so  hot  to  us  as  in  dry  weather.  In  arid  coun- 
tries or  at  high  elevations  (as  at  Santa  Fe  or 
the  city  of  Mexico,  each  about  seven  thousand 
feet  above  the  sea)  there  is  little  moisture  in 
the  air,  and  the  sun's  rays  are  in  summer  so 
strong  that  passing  from  the  shady  to  the 
sunny  side  of  the  street  is  almost  like  receiving 
a  blow.  At  lower  levels,  especially  in  a  moist 
climate,  as  in  Florida,  the  distinction  between 
shade  and  sunshine  is  not  so  marked.  At  the 
same  time  the  air  becomes  more  heated  in  the 
moist  climate,  so  that  the  house  does  not  fur- 
nish so  much  comfort  and  the  moisture  obstructs 
the  evaporation  from  the  surface  of  the  body. 
When  the  sun's  rays  seem  unusually  hot  and 
burning  and  the  shade  unusually  cool,  it  is  a 
sign  that  there  is  little  moisture  in  the  air. 

Moisture  also  has  an  effect  on  the  acoustics 
and  transparency  of  the  air.  One  can  hear 
and  see  farther  in  quiet  moist  air  than  in  dry. 
This  is  probably  an  indirect  effect  due  to 
the  settling  of  the  motes  of  the  air.  These? 
although  individually  invisible,  give  the  air 
a  sort  of  turbidity  which  lessens  both  its 
capacity  for  conveying  sound  and  its  transpar- 
ency, but  the  motes  are  capable,  in  many  cases, 
of  absorbing  moisture,  and,  in  all  cases,  of  hav- 
ing it  condense  on  them.  This  increases  their 


SIMPLE  RESULTS  OF  WEATHER  CHANGES.     235 

weight  and  causes  them  to  settle.  A  center  of 
high  pressure  with  settling  air,  if  not  too  long 
continued,  has  the  same  effect  by  replacing 
the  dusty  air  at  the  surface  by  the  clearer  air 
from  above,  rendered  also  denser  by  its  motion 
downward. 

Thus  the  downward  motion  in  the  high 
brings  at  first  purer  air  in  which  sounds  can  be 
heard  with  remarkable  distinctness,  especially 
from  hill  to  hill.  Such  a  transparency  to  sound 
is  rather  a  sign  of  settled  weather  than  of 
change.  If,  however,  a  high  remains  long  over 
one  place,  it  promotes  by  its  dryness  and  calm- 
ness the  formation  of  dust,  and  thus  in  time  in- 
creases the  turbidity  of  the  air. 

The  low  improves  the  drafts  of  chimneys, 
because  the  air  it  brings  is  generally  nearly 
calm,  and  the  contrast  in  temperature  between 
the  heated  air  from  the  flue  and  the  outer  air 
enables  the  latter  to  rise.  A  low  also  im- 
proves the  draft  near  its  center,  for  then  there 
is  a  marked  tendency  upward,  but  the  horizon- 
tal currents  tend  to  draw  the  column  of  smoke 
to  one  side.  When,  therefore,  the  column  of 
smoke  rises  to  some  height  straight  in  the  air, 
it  usually  indicates  the  presence  of  a  high  with 
prospects  of  calm  and  sunny  weather.  In  gen- 
eral, the  presence  of  a  high  improves  the  sym- 

17 


236  ABOUT  THE  WEATHER. 

metry  of  the  column  of  smoke,  but  that  of  a 
low  improves  the  draft. 

The  low  also  draws  air  from  the  earth,  from 
mines,  and  from  drains.  In  the  mines  the  effect 
is  to  draw  out  inflammable  gases,  increase  the 
amount  of  coal  dust,  and  so  make  destructive 
explosions  more  probable.  By  drawing  the  air 
out  of  the  soil  it  permits  the  soil  waters  to  rise 
and  increases  the  flow  of  springs  and  the  height 
of  water  in  wells.  Indeed,  some  wells  have 
been  found  to  be  good  barometers.  By  draw- 
ing air  out  from  the  drains  and  sewers  an  ap- 
proaching low  heralds  itself  by  the  bad  odors 
which  it  calls  out. 

As  summer  local  storms,  and  even  a  great 
general  storm,  if  intense,  approach,  all  Na- 
ture is  seized  with  a  sort  of  unrest.  The  ani- 
mals, perhaps  most  affected  by  the  increasing 
moisture,  perhaps  by  an  instinctive  knowledge 
of  danger  approaching,  go  through  with,  a 
series  of  actions  unusual  to  them.  These  are 
especially  noticeable  with  our  friends  and  near 
acquaintances,  the  domesticated  animals — the 
dog,  cat,  horse,  cow,  hog,  goat,  fowls — each  one 
of  which  has  its  own  signs  of  unrest  and  anxi- 
ety. The  bees  hasten  home  and  there  show  a 
state  of  great  excitement,  while  the  ants  hurry 
the  closing  of  the  outer  gates  of  their  subterra- 


SIMPLE  RESULTS  OF  WEATHER  CHANGES.     237 

nean  city.  Even  man  feels  some  of  the  mental 
excitement,  while  his  physical  system  reminds 
him  of  his  gout  or  rheumatism  or  neuralgia, 
and  the  plants  rustle  their  leaves  as  if  they, 
too,  had  nervous  tremors.  The  lightning 
flashes ;  the  rain  or  hail  rattles ;  the  air,  at 
first  tremulous  and  sending  up  the  leaves 
and  dust  in  little  whirls,  then  settling  down 
to  a  good  fresh  blow,  now  becomes  calm  for 
a  few  moments.  The  rolling,  heaving  clouds 
pass  by,  the  sun  comes  out  suddenly  and  shines 
with  renewed  energy,  and  a  gentle  breeze 
springs  up  from  a  new  quarter.  The  storm  is 
over,  all  nature  is  again  cheerful,  and  the  ani- 
mals return  to  their  usual  pursuits. 

There  is  one  sign  of  approaching  wind 
which  is  usually  neglected,  and  that  is  the 
twinkling  of  the  stars.  This,  it  has  been 
proved  of  late  years,  is  due  to  winds  in  the 
upper  atmosphere  which,  by  changing  and 
breaking  up  the  uniformity  of  the  air,  cause 
some  such  variations  in  the  light  as  are  seen  in 
the  air  rising  from  a  hot  stove.  Now,  a  high 
wind  in  the  upper  air  is  likely  to  descend, 
hence  the  twinkling  is  a  sign  not  only  of  winds 
above,  but  of  winds  likely  to  appear  soon  at 
the  surface  of  the  earth. 

The  size  of  the  crystals  of  snow  is  an  in- 


238  ABOUT  THE  WEATHER. 

dication  of  the  temperature  where  they  are 
formed.  The  larger  the  crystal  the  higher  the 
temperature,  and  the  lowest  temperatures  in 
which  snow  is  formed  are  those  where  the  crys- 
tals are  minute  sharp  needles  like  those  in  a 
blizzard. 

The  best  of  all  indicators  of  the  weather, 
however,  is  the  barometer.  The  pressure  of 
the  air  is  the  simplest  meteorological  element 
and  the  one  most  indicative  of  ascending  and 
descending  currents  of  air ;  and  these  are,  as  we 
have  seen,  the  necessary  phenomena  of  storms— 
the  more  marked,  the  more  intense  the  storm. 
For  one  who  wishes  to  study  the  weather 
changes  seriously,  or  whose  comfort  or  interest 
depends  on  knowing  them  as  long  beforehand 
as  possible,  a  good  barometer  is  indispensable. 
If  it  is  desired  to  make  these  changes  visible  in 
a  schoolroom,  the  great  glycerin  barometer 
will  give  the  best  results.  A  series  of  mirrors 
could  be  easily  arranged,  which  would  bring 
down  the  head  of  the  column  and  make  it 
visible  in  a  large  hall  by  every  one  in  the  as- 
sembly. 

Should  any  reader  of  this  book  wish  to 
continue  his  studies  of  the  weather,  and  to  take 
regular  observations,  his  best  way  is  to  write 
to  the  Section  of  the  Crop  and  Weather 


SIMPLE  RESULTS  OF  WEATHER  CHANGES.     239 

Service  of  his  State,  and  join  its  staff  of  ob- 
servers. He  will  then  perhaps  be  provided 
with  certain  instruments,  and  with  sheets 
for  registration  and  full  instructions  for  mak- 
ing his  observations.  He  may  also  have  the 
satisfaction  of  knowing  that  his  observa- 
tions will  be  useful  to  others  than  himself, 
and  that  the  results  will  be  published,  and  he 
will  receive  not  only  these  publications,  but 
others  that  will  be  useful  to  him.  For  a  yet 
more  advanced  study  a  set  of  registering  instru- 
ments will  be  needed,  and  these  must  be  ob- 
tained from  the  dealers  in  such  articles. 


INDEX. 


Accumulation  of  poisonous  prod- 
ucts of  life,  12,13. 
Air-brakes,  37. 

Air,  currents  ascending    and   de- 
scending, 51. 

experiments  with,  221-231. 

how  a  particle  is  made  to  take  a 
contra-clockwise  spiral  in  en- 
tering a  cyclone,  141. 

resistance  to  anything  moving  in 
it,  25-29. 

weight  of,  33-35. 

(atmospheric)  pressure,  at  sea 
level,  35. 

changes  in,  41-43. 

experiment  to  show,  38. 

healthy  human  body  not  sensi- 
tive to  changes  of,  46. 

highest  and  lowest  over  the 
oceans,  43. 

how  measured,  33-40. 

measured  by  a  mercurial  barome- 
ter, 38. 

permanent  centers  of,  43. 
Anemometer,  or  Robinson's  cups, 

57. 

Aneroid,  how  made,  39. 
Anticyclones,  or  highs,  142. 

air  pressure  uniform  for  a  large 
area  during,  143. 

dryness  connected  with,  145. 

eastward  motion  of,  145. 


Anticyclones,  or  highs,  sunstrokes 

apt  to  occur  during,  147. 
weather  connected  with,  146. 
winds  connected  with,  144. 
Anti-trade  winds,  140. 
Architecture,  7. 
Atmosphere,  depth  of,  41. 
how  affected  by  the  earth's  rota- 
tion, 136. 

Balloon  ascent  by  Glaisher,  47. 

as  a  weather  prophet,  220. 

toy  as  a  barometer,  224. 
Barometer,  aneroid,  39. 

balance,  225. 

best  weather  indicator,  238. 

mercurial,  38. 

others,  39. 
Blizzard,  153. 

Bone  beds  in  the  Western  plains, 
18. 

Candlemas  Day,  192. 
Carbonic-acid  gas,  13. 
Chimneys,  draft  improved  by  lows, 

235. 

Cities,  7. 

crowded  dwellings  in,  12. 
cost  of  cleaning  streets  of,  21. 
Clockwise  and  anti-clockwise  rota- 
tion of  winds,  lOo. 
Cloud-bursts,  174-177. 
241 


242 


ABOUT  THE  WEATHER. 


Clouds,  cumulus,  85. 

cirrus,  81. 

cumulus,  how  formed,  111. 

filly's  tail,  83. 

formed  by  expansion  of  air,  46. 

forms  and  names  of,  81. 

heights,  how  found,  80. 

mackerel  backs,  83. 

nimbus,  91. 

rain,  develop  electric  tension,  97. 

represent  a  relation  between  tem- 
perature and  humidity,  78. 

stratus,  or  blanket,  87. 
Coast  weather,  194, 195. 
Coldest  days  of  the  year,  191. 
Cold  waves  in  the  south,  152. 
Conquest  of  forests,  3. 
Contest  of  man  with  animals,  2,  3, 

of  man  with  climate,  2. 

of  man  with  germs  of  disease,  2. 

of  man  with  rocks  and  soil,  2. 

of  man  with  weather,  2,  4-8. 
Continental  weather,  194. 
Currents  of  the  ocean,  how  affected 

by  the  earth's  rotation,  139. 
Cupping,  or  bleeding,  36. 
Cyclones,  99-109. 

cloud  caps  of,  114. 

customary  route  and  rate  of  speed 
across  North  America  of,  121. 

considered  as  steam  engines,  110- 
116. 

customary    route    across    South 
America  of,  122,  123. 

diagram  and  model  of,  109. 

efficient  cause  for  eastward  move- 
ment of,  124-127. 

how  long  they  last,  123. 

how  they  begin,  117, 118. 

paths  of,  in  North  America,  118. 

Dangerous  diseases  brought  on  by 
excessive  sensitiveness  to  cold, 
11. 


Disease  germs,  3,  4. 
creatures  of  climate,  filth,  and  the 

weather,  4. 
dangerous  in  the  tropics  and  in 

damp,  dark  places,  14. 
in    a    natural    condition    would 
have    little    power  to    injure, 
14. 

how  they  spread,  15. 
Dew,  73-75. 

falls  when  the  air  is  calm,  74. 
Development  of  the  fine  arts,  7. 
Drawbacks  of  the    protection    of 
man    from    the    weather,    9- 
16. 

Dust  universally  present,  15. 
Dust-whirls,  how  made,  49,  50. 
Dwellings,  6. 
crowded  in  a  city,  7-12. 
necessity  of  improvement  of,  be- 
stows the  chief   stimulant  to 
mechanic  arts,  7. 

Dyrenforth  experiments  in  making 
rain,  30. 

Eddy,  William  A.  Experiments 
with  kites,  216-220. 

Electric  waves,  32. 

Electrical  discharges,  180-186. 

Electrical  condition  of  atmosphere 
important  in  the  trade  in  in- 
formation for  journalistic  pur- 
poses, 20. 

Electricity,    its    part    in    weather 

changes,  97. 

the  use  of,  suffers  from  exposure 
to  the  weather,  22. 

Equator  heat,  movements  of,  53. 
heat,     accompanied     by     calm 
weather,  53. 

Evaporation     always     going     on 

everywhere,  69. 
governed  by  temperature,  70. 

Evaporimeter,  231. 


INDEX. 


243 


Fine  arts,  development  of,  result 

of  weather  contest,  7. 
Foehn,  200. 
Fog,  195. 

and  clouds  one  and  the  same,  79. 
causes    dangerous    delays,    how 

they  are  remedied,  30. 
in  London,  196. 

in  winter,  composed  of  ice  crys- 
tals, 96. 
Forests,  how  they   afl'ect    climate 

and  weather,  201,  202. 
Frost  injures  freight,  20. 
injures  telegraph  poles,  24. 

Germs  of  disease  creatures  of  filth 

and  climate,  14. 

of  disease  dangerous  in  the  heat 
of  the  tropics  and  in  damp, 
dark  places,  14. 

of  disease  in  a  natural  condition 
have  little  power  to  injure,  14. 
of  disease  living  in  the  air,  76. 
of  disease,  how  they  spread,  15. 
Glaisher  ascended  to  height  of  37,- 

000  feet  in  a  balloon,  46. 
Gymnastics,  12. 

Hail,  how  formed,  171-173. 
Hailstones,  shapes  and  sizes,  171. 
Hailstorms,  166-168. 
amount  that  falls  in  a  storm,  170- 

173. 

destructive  effects  of,  172. 
Heat  equator,  188. 

how  absorbed  and  lost,  61. 
hottest  days  of  the  year,  193. 
much  of,  in  the  sun's  rays  lost 
at  upper  surface  of  clouds,.  61. 
Highs,  or  anticyclones,  142-147. 
Hoarfrost,  dew  deposited  at  tem- 
peratures below  freezing  point, 
74. 
Home,  6. 


House,  6. 
Humidity,  66-72. 

absolute,  71. 

how  measured,  72. 

what  it  is,  66. 

Hurricanes,  how  they  are  made, 
50,  51. 

Ice  storms,  166. 

Information,  trade  in,  for  journal- 
istic purposes,  20. 

Isobars,  100. 

change  made  to  reduce  them  to 
sea  level,  42. 

Isotherms,  65. 

Jefferson,  Thomas,  first  to  attempt 
simultaneous  weather  observa- 
tions, 212. 

Jenner,  Dr.,  203. 

Kites  as  aids  in  acquiring  knowl- 
edge of  the  weather,  215,  216, 
220-222. 

Lakes,  currents  in  the  Great,  af- 
fected by  the  rotation  of  the 
earth,  138-140. 
Landscape  gardening,  7. 
Langley,    experiments    with    bal- 
loons, 220. 
Lightning,  183-186. 
injures  telegraph  wires  and  poles, 

23. 

partial  use  of  arresters,  23. 
sets  fire  to  buildings,  23. 
Local  influences  on  the  weather, 

194-202. 
Lows,  99-109. 

increase  the  probability  of  ex- 
plosions in  mines,  236. 
sometimes  formed  from  the  re- 
mains of  old  ones,  118. 
Luxury  developed  by  modern  civ- 
ilization, 15. 


244 


ABOUT  THE  WEATHER. 


Matter  forms  in  which  it  exists,  66. 
Mechanic  arts  take  their  rise  from 
the    necessity    of    protection 
against  the  weather,  7. 
Moisture  or  humidity,  66. 
effect  upon  sound,  234. 
effect  upon  transparency  of  the 

atmosphere,  235. 
measured  by  a  hair,  228. 
quality  of  atmosphere    changed 

by  amount  of  present,  233. 
Monsoons,  191. 
render  predictions  of  the  weather 

for  the  seasons  possible,  21 6. 
Mountains    as    controllers    of  the 
weather,  196-200. 

Neglect  of  physical  activity  in 
modern  civilized  life,  11. 

Northers  of  Texas,  how  they  arise 
and  the  injury  they  cause,  151. 

Ocean  currents,  how  affected  by 

the  rotation  of  the  earth,  139. 
Office  buildings,  7. 

Particles  afford    the   nucleus    for 

droplets  of  cloud  or  fog,  77. 
given  off  from  warm  solids  and 

burning  objects,  76. 
in  volcanic  eruptions,  76. 

Pendulum  motion  affected  by  the 
earth's  rotation,  138. 

Piche,  inventor  of  evaporation  in- 
struments, 230,  231. 

Plows,  snow,  on  locomotives,  29. 

Poisonous  gases  collected  as  a  re- 
sult of  protection  from  the 
weather,  14. 

Polar  weather,  214. 

Poverty  made  more  difficult  to  avoid 
by  development  of  the  needs 
of  modern  civilized  life,  16. 

Precipitation,  92-98. 


Progress  in  knowledge  of  the 
weather,  211-222. 

Projectiles,  swiftness  compensates 
for  yielding  quality  of  sub- 
stance of,  93. 

Protection  from  ordinary  weather 
not  sufficient  in  case  of  ex- 
traordinary, 17. 

afforded  by  houses  and  garments 
often  more  than  sufficient,  10. 

Pump,  suction,  35. 

Rain,  attempt  to  produce,  by  artifi- 
cial- means,  30,  31. 
evaded,  4. 
in  a  cyclone,  116. 
miscalculations  as  to  amount  of, 

17. 

symptoms  of  coming,  203-206. 
Rainy  season  in  the  United  States, 

190. 

Relation  of  rainfall  to  sewers,  17-20. 
Symptoms  of  coining  rain,  203-206. 
Remedy  for  oversensitiveness  to 

cold,  22-32. 

Roof,  improvements  in,  4. 
Rotation  of  the  earth,  effect  upon  a 
body  moving  horizontally  upon 
or  parallel  to  its  surface,  137, 
138. 

Savages,  free  from  artificial  sensi- 
tiveness, 9. 

find  few  things  indispensable,  15. 
return  to  savage  simplicity  im- 
possible, 16. 

Scientific  modern  methods  of 
weather  forecasts,  206. 

Sculpture,  7. 

Section  of  currents  of  air  in  a  cy- 
clone, 107. 

Sewer  gas,  13. 

Signs  of  rain,  203,  206. 

Silence,  areas  of,  during  a  fog,  30. 


INDEX. 


245 


Simple  results  of  weather  changes, 

232-239. 
Sleet,  168. 
Snow,  168-170. 
beneficial  to  farmers,  94. 
brooms  on  street  cars,  29. 
fall,  its  equivalent  in  water,  94. 
flakes,  beautiful  forms  of,  95. 
necessity  of  using  pick  and  blast 

for  removing,  29. 
obstructs  traffic,  21. 
plows  on  locomotives,  29. 
Sound  shadows  due  to  rocks,  etc., 

30. 
Storms,  general,  cyclones,  or  lows, 

99-109. 
local,  unrest  occurring  at  approach 

of,  236. 

parallel  ribbon,  154. 
region  of  local,  189. 
same   sort  as    those   which   de- 
stroyed animals  whose  fossil  re- 
mains are  found  in  the  Western 
plains,  18. 
Summer,  Indian,  193. 

Telegraph,  connected  with  trade 
in  information  for  journalistic 
purposes,  20. 

indispensable    in  weather    fore- 
casts, 213. 
Telephone,  a  remedy  for  danger 

caused  by  fogs,  30. 
Temperature,    absolute    range    of, 

63,  64. 

highest  and  lowest  known,  63. 
how  measured,  64. 
in  cyclones,  102. 
lowest  at  night,  63. 
modified  by  clouds,  63. 
tenement-house,  7- 
Thermometers  of    different    sorts 

described,  64. 
of  whalebone  and  steel,  227. 


Thunder,  186. 
Thunderstorms,  174-179. 
the     conditions     under     which 

they  occur,  174,  175. 
Tornadoes,  156-165. 
accompanied    by   funnel-shaped 

cloud,  158. 
course    taken     in    the    United 

States,  190. 
damages  by,  162. 
extent  of,  164. 
photographs  of,  160. 
phenomena  connected  with,  1('»2. 
their  relations  to  cyclones,  156- 

158. 

what  they  are,  156. 
when  and   how  often,  likely  to 

occur,  164. 

where  most  likely  to  form,  158. 
Trade  winds,  Anti-,  140. 
how  they  are  formed,  53,  54. 
transportation  by  land,  enormous 

development  of,  19. 
sensitive  to  weather  changes,  19. 

Ventilation,  best,  an  open  fireplace, 

13. 
difficult  to  manage  in  winter,  13. 

Verification,  percentage  of,  in  mod- 
em scientific  weather  fore- 
casts, 208. 

Volcanoes,  eruption  in  the  Straits 
of  Sunda,  76. 

Vortex,  double,  for  each  hemi- 
sphere, 140. 

Water,-  carrier  and  distributor  of 
heat  in  the  atmosphere,  68. 

comes  from  evaporation,  69. 

only  natural  and  common  sub- 
stance that  changes  its  phys- 
ical state  in  the  range  of  me- 
teorological variations,  67. 

spouts  caused  by  tornadoes,  158. 


246 


ABOUT  THE  WEATHER. 


Weather,  accurate    prediction   of, 

attempted,  23. 
alternations  of,  through  the  day 

and  year,  187-193. 
artificial,  30. 
creation  of  dwellings  result  of 

contest  with,  6. 
danger  to  sailors  and  steam  navi- 

gators from,  18. 
drawbacks  connected  with  pro- 

tection from,  9-16. 
enormous  amount  of  work  done 

by  the,  92. 

exploration  in  the  upper  air,  222. 
fine  arts  developed  by  the  ne- 

cessity of  protection  from,  7. 
following  a  cyclone,  128-135. 
for  which  we  are  not  prepared 

oftenest  met  with  by  persons 

engaged  in  open-air  pursuits, 

18. 
forecasts,  ^  a  remedy   against  in- 

juries by  the  elements,  203-210. 
how  predicted  as  a  low  comes 

on,  132. 
intermediate,  149-155. 

characteristics  of  the  tropics, 
148. 

gales  prevailing  during,  149. 
man's  contest  with,  2. 
map,  101. 
necessity  of  protection  from,  af- 

fords mechanic  arts  their  chief 

stimulus,  7. 

of  a  brewing  storm,  134. 
of  a  dry  region  under  a  high? 

201. 

prediction  by  weather  signs,  31. 
predictions  based  upon  map,  207. 

to  be  of  use    must  promptly 
reach  those  who  are  to  be 
benefited  by  them,  210. 
remedy  against  injuries  by,  23- 


Of    THE 


Weather,   service,    cost    per    an- 
num   in    the    United    States, 
209. 
dry    predictor,   consisting    of   a 

dancing  girl,  229. 
what  contest  with,  has  done  for 

man,  8. 
Wedge  wood,  inventor  of  a  toy  horse 

moved  by  the  weather,  230. 
Windmills,  rule  for  calculating  ef- 
ficiency of,  58,  59. 
Winds,  Chinook,  199. 
direction,  velocity,  and  measure- 
ment of,  56-59. 
due  to  the  tendency  of  air  to 

equalize  its  pressure,  48,  49. 
horizontal,  53. 

hot,  in  Western  regions,  153. 
in  a  cyclone,  103. 
on  land  and  sea,  187, 188. 
measured  by  a  toy  windmill,  227, 

228. 

rings  on  the  earth,  54,  55. 
succession  of,  during  passage  east- 
ward of  a  general  storm,  129- 
132. 
their  kinds  and  distribution,  48- 

54. 

trade,  140. 

how  they  are  formed,  and  how 
they  obtain  their  name,  53, 
54. 
twinkling  of  the  stars  a  sign  of 

approaching,  237. 
Wireless  telegraphy,  32. 
Wires,  telegraphic,  hoarfrost  upon, 
24,25. 

liable  to  be  struck  by  light- 
ning, 22. 

weak    point  or  break  in,  in- 
volves danger  at  the  receiv- 
ing instruments,  23. 
Woodchuck  as  a  weather  prophet, 
182. 

(7) 


APPLETONS'  HOME-READING  BOOKS. 

Edited  by  W.  T.  HARRIS,  A.M.,  LL.D.,  U.  S.  Commissioner  of  Education. 

The  purpose  of  the  HOME-READING  BOOKS  is  to  provide  wholesome, 
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Year.  (ALPHABETICALLY  BY  AUTHORS.)  Cents. 

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7th.  Uncle  Sam's  Secrets.  By  O.  P.  Austin  75 

6th.  Uncle  Sam's  Soldiers.  By  O.  P.  Austin  .  75 

7th.  The  Story  of  the  Birds.  By  J.  N.  Baskett  .  .  65 

6th.  The  Story  of  the  Fishes.  By  J.  N.  Baskett  .  .  75 

6th.  The  Story  of  the  Amphibians  and  Reptiles.  By  J. 

N.  Baskett  and  R.  L,  Ditmars 60 

5th.  In  Brook  and  Bayou.  By  Clara  Kern  Bayliss  .  .  60 

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6th.  Historic  Boston  and  its  Neighborhood.  By  E.  E.  Hale  50 

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7th.  The  Story  of  Rob  Roy.  By  Edith  D.  Harris  .  .  60 

4th.  The  Earth  and  Sky.  By  Edward  S.  Holden  .  .  28 

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3th.  Chronicles  of  Sir  John  Froissart.  By  A.  Singleton  .  75 

5th  The  Plant  World.  By  Frank  Vincent  60 

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The  Twentieth  Century  Spellers. 

In  two  books. 

By  WM.  L.  FELTER,  Ph.D.,  Principal  of  the  Girls* 
High  School,  Brooklyn,  N.  Y.,  formerly  Associate 
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The  authors,  in  presenting  this  series  of  spellers  to  the  public, 
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book,  as  in  many  cases  the  words  selected  from  the  reading  lessons 
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country  have  been  consulted  and  these  books  have  been  compiled 
for  general  use. 

"The  Twentieth  Century  Spellers.  By  William  L.  Felter,  Ph.D., 
and  Libbie  J.  Eginton. 

"Book  One.  This  book  is  planned  on  the  supposition  that  oral 
spelling  should  not  be  required  until  the  beginning  of  the  second  year. 
The  pupils  will  be  asked  to  copy  only  those  words  and  sentences  which 
they  have  first  been  taught  to  read.  It  is  suggested  that  the  daily 
lessons  for  the  first  half  of  the  second  year  do  not  exceed  three  new 
words,  and  for  the  second  half  four  new  words.  This  speller  covers  the 
first  four  years  of  school.  Sentences  to  be  read  and  copied  accompany 
every  spelling  lesson. 

"  Book  Two  covers  the  remaining  four  grades,  including  the  eighth. 
The  same  plan  is  followed  as  in  Book  One.  Poems  from  standard 
authors  are  introduced  in  this  as  reading  lessons.  The  use  of  the  dic- 
tionary is  recommended  for  getting  definitions." 

— New  York  Primary  Education. 

"This  is  an  admirable  spelling  book." — Boston  Journal  of  Education. 
D.  APPLETON  AND  COMPANY,  NEW  YORK. 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


AN     INITIAL    FINE      OF     25     CENTS 

WILL  BE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  5Q CENTS  ON  THE  FOURTH 

^•k.   V.   1 THE  SEVENTH  DAY 

OVI 


27  I 


APR    13  1943 


SENT  ON  Hi. 

MAY  08  2081 

U.C.  BERKELEY 


LD  21-50m-8,-32 


• 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


